1.) which relation is a function? a {(–3, 4), (–2, 5), (0, 9), (0, 12)} b. {(8, –1), (2, –1), (3, 8), (2, 5} c. {(7, 12), (1, –5), (3, –10), (2, –5)} d. {(1, 2), (1, 5), (1, –1), (1, 4)} 2.)which relation is a function?

1)  A function won't have repeats of the x values . Thus the first choice will not be a function because of the 2 '0' x values.
C is the answer to thid question

2)  The first choice A is the only  function. It is the only one which passes the vertical line test.  ( if we can draw any vertical line which passes through more than one point on the graph then its is NOT a function).

A= r2 × 3.14 7x7 ↓ ↓ 49 × 3.14 = 153.86 → 153.9