How do I solve these?

Which exponential functions represent exponential decay?

Select all that apply.

f(x)=(0.85)xf of x is equal to 0 point 8 5 to the x th power , ,

f(x)=(0.95)2xf of x is equal to 0 point 9 5 raised to the 2 x power , ,

f(x)=1.8(0.6)xf of x is equal to 8 times 0 point 6 to the x th power , ,

f(x)=(1.01)xf of x is equal to 0 1 to the x th power , ,

f(x)=0.25(1.5)3x