That's definitely an example of exponential decay, since the base (1/2) (also called the "common ratio") is greater than 0 but less than 1.

Positive square root of 0.25 = 0.5
Hope this helps. - M
a: 2
b: 5
c 3
d: 4
I think the ans is 2
A parallelogram has two pairs of opposite sides. A trapezoid only has one pair of parallel sides.