Answer:
Option B and D are represents the equation model exponential decay.
Step-by-step explanation:
Exponential decay function is in the form of : where a is the initial value and b≠0, 0<b<1.
Option A:
here a = 6 and b = 2.1 > 1
It is not an exponential decay
Option B
here a = 0.34 and b = 0.98<1
Therefore, It is an exponential decay.
Option C:
here a = 0.75 and b = 1.21 > 1
It is not an exponential decay
Option D:
here a = 8 and b = 0.28<1
so, it is an exponential decay.