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HN) Exercises (1)You take 200 milligrams of a headache medicine, and after 4 hours, 120 milligrams remain in your system. If the effects of the medicine wear off when less than 80 milligrams remain, when will you need to take a second dose, assuming the anmount of medicine in your system decays exponentially? 13 ส.ค. The half-life of Radium-226 is 1590 years. If a sample initially contains 200 mg. how many milligrams will remain after 1000 years? )The half-life of Fermium-253 is 3 days. If a sample initially contains 100 mg, how many milligrams will remain after 1 week? บ้อ The half-life of Erbium-165 is 10.4 hours. After 24 hours a sample still contains 2 mg. What was the initial mass of the sample, and how much will remain after another 3 days? The half-life of Nobelium-259 is 58 minutes. After 3 hours a sample still contains10 mg. What was the initial mass of the sample, and how much will remain after another 8 hours? (6) A scientist begins with 250 grams of a radioactive substance. After 225 minutes, the sample has decayed to 32 grams. Find the half-life of this substance. A wooden artifact from an archeological dig contains 60 percent of the carbon-14 that is present in living trees. How long ago was the artifact made? (The half-life of carbon-14 is 5730 years.)

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Revision (Units 1-3) 100 Circle the correct item. 1 they want to go to the theatre? 14 Ben lives in a nice flat. It belongs to . father. * ๑๑ ๑ ๑ A Does B Do C Are A he B him C his 2 He usually . his homework in the afternoon. 15 We're ptaying football. Do you want to join ...? A do B does C doing A we B them C us 3 This is me and Mary. . . are both twenty. 16 This is Cathy and Carol. . are sisters. C Their A They B You (c) We A They B Them 4 Lucy . a cup of coffee every morning. A is having B have . is Jack going? To the supermarket. B Why 17 C has A What C Where 5 Our neighbours spenda lot of time in . . 18 Mary is . on time for work. She's never late. garden. A usually B seldom C) always A they're B they C their 19 We . basketball in half an hour. 6 people are there in the picture? Two. A play B are playing C plays A How many B How much C How often 20 This is the train . . goes to London. 7 The girl . is standing over there is my cousin. A who B which C where A which B who C where 21 How . is the bus stop from here? 8 Bill . goes to the gym; he doesn't like it. A old B far C long A usually B always C never 22 That's the cottage *. . * we spend our summer 9 is that man? He's my dad. holidays. A How B Where C Who A who B which C where 2 How . ..do you go to the cinema? 23 . he work at weekends? A rarely B often C usually A Do B Is Does . piano lessons three times a week. B is having He 24 is John from? Dublin. *๑๑๑๑๑๑ ๑ A has C have A Where B Which C What My best friend . in Rome at the moment. 25 Are you anything tonight? A (ive B lives C is living A do B does C doing Do you know John? He's brother. A mine B my C me

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Part One: Grammar Items 1 - 15: Error recognition Instruction: Read the following statements and choose the underlined part that is grammatically wrong. Objective: Students can be able to classify passive form. Items 1 - 15: Error recognition 1. The first time of motorcycle race on record in Thailand take place in 1960. 1 2 3 4 2. For the world's starving millions, find enough food to keep body and soul together 1 2 3 has become the paramount concern in life. 4 3. I hadn t know the bad news when he told me. 1 2 3 4 4. A high rate of TV watching among children in poorer suburban areas and in the 1 provinces, compared to those living in large urban centers, is often because poverty 2 4 and lack of other kinds of entertainment in the area. 5 5. Jenny told Christina that he would look forward to see him soon. 1 2 3 4 6. Famous novel on mental disorders are being continually supplemented by dramatic 1 2 3 presentations in the theaters, in the movies, and on television. 4 7. The number of students want to pass the examination. 1 2 3 4 8. Deep sea fish are well adapted to their environments, but they have not yet learned 1 2 what to avoid their greatest predator - man. 3 4 9. Natural selection defines as the process that directs the course or evolution by 1 2 preserving those traits best adapted for an organism's survival. 3 4

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Present Perfect and Past Simple USE YOUR NOTES if you need them! 1. If the first sentence is true, do we know that the second sentence is true? In the box write "yes" (the sencond sentence is true) or "don't know" (because we don't know if the second sentence is true or not). Vincent grew a beard. Vincent has a beard now. My dog has eaten her food. Sarrah opened the door. Ulysse lost his homework. Camille has closed the window. There is no food in the bowl now. The door is open now. His homework is lost now. The window is dosed now. Ilona is on vacation now. Clemence is on the phone now. Ilona has gone on vacation. Clemence phoned her friend. Alexis has grown a mustache. Ginger has been to Spain. Yibing has gone to Italy. Alexis has a mustache now. Ginger is NOT in Spain now. Yibing is in Italy now. 2. Write the past simple or present perfect form of the verb in parentheses into the blank space. DO NOT use contractions (ve gone, didntknow, etc.). A. Last night I (lose) my apartment keys. I had to phone my roommate to let me in. B. I (lose) my keys! Can you help me look for them, please? C. Kelsey D. Kelsey E. Angela F. Carla G. (be) There (go) to Dublin to live 3 years ago. (live) in Dublin for 3 years. (not go) to work yesterday. (not be) to school today. a lot of accidents last year, and there a lot of accidents this year, too. |not 1. (make) Our factory not her yesterday. Jeannie yet today, and I more than 10,000 motorcycles this year; it H. (see) 1 not | as many last year. 3. (earn) John a lot of money this year - much more than he last year. not for K. (stop) Benjamin five years. smoking five years ago. (smoke) He L. (win) Our lacrosse team is very good. We | the state championship last year, and the national championship this year. not we M. (work) Randy last month, but he hard this month. Is he working hard or hardly working? N. (be) I am Worried about Laetitia. She most of this week, too. not | ill last week, and she ill 0. (รnow) It much last year, and it not much this year either. P. (visit) you ever Alaska? Yes, I there several times on vacation. I love the winter cruise!

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