Please help!!!

**Answer:**

D 10 is the size of the sample at the time it was discovered

**Step-by-step explanation:**

An exponential equation is written in the form

y = ab^x

where a is the initial value

b is the growth or decay

x is the amount of time

y = 10 (.5)^x

10 is the initial value

.5 is how fast it is decaying (50 % decay rate)

x is the time in days