Answer: a and d
Explanation:
First of all, we need to make a analysis of each letters:
a. factoring 32 = 2.2.2.2.2 = 

 

then, 
16 = 

but 

in conclusion that, this inequality is correct
b. 27 = 

this first situation is equal to 

the second situation is:
81 = 

and 

it's a mistake.
c. factoring 9: 

 
 <
 < 

it's wrong.
d. factoring 8 = 

factoring 32 = 

 
 >
 > 

This is true.
Finally.. our correct answers is a and d.