Question

あ

(1)と(4)を教えてください

3 〔it... to ~ の構文〕 次の (1), (2)はItで始めて, (3), (4) は仮目的語 it を使って書きかえよ。
To work in this office is pleasant.
It is pleasant of you to work in this office
She kindly showed me the way.
It is kind of her to show me the way.
(3) I found that to solve the problem was difficult.
I found it difficult to solve the problem
(4)I think that to sleep well is necessary.
I think it necessary to sleep well

Answer 1

taka

(1) It is pleasant for you to work in this office. このオフィスで働くのは楽しい。
(4) I(S) think(V) it(O 形式目的語) necessary(C) <to sleep well>(真目的語).　ぐっすり眠ることは必要だと思う。[第5文型]
＝ I think (that)(省略可) it is necessary to sleep well.
※I think it is necessary to sleep well. は、英文としては間違いではありません。
ただ、出題者の意図は(3)と同じように第5文型にして欲しいだけです。

参考にしてください。