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