Question

ろぐちゃん

九番がわからないので教えてください🙇‍♀️ちなみに2枚目が答えです。特にDがなぜダメなのかを教えて欲しいです。

In Exercises 9 and 10, which sets of ordered pairs represent
functions from A to B? Explain.
9. A = {0, 1, 2, 3} and B = {-2, -1, 0, 1, 2}
(a) {(0, 1), (1, − 2), (2, 0), (3, 2)}
-
(b) {(0, − 1), (2, 2), (1, − 2), (3, 0), (1, 1)}
(c) {(0, 0), (1, 0), (2, 0), (3, 0)}
(d) {(0, 2), (3, 0), (1, 1)}

9. (a) Each element of A is matched with exactly one
element of B, so it does represent a function.
(b) The element 1 in A is matched with two
elements, -2 and 1 of B, so it does not
represent a function.
(c) Each element of A is matched with exactly one
element of B, so it does represent a function.
(d) The element 2 of A is not matched to any
element of B, so it does not represent a
function.