Review the table showing the mass of a radioactive isotope over time.

Time (Seconds)

Mass (Grams)

2

10.5

5

8.5

8

7

10

6

15

4.5

18

3.5

Which function best models this data?

y = 11.97(0.93)x
y = –0.42x + 10.75
y = 13.15 – 3.17 ln x
y = 0.01x2 – 0.72x + 11.82