Answer:
C.A 30 kg suitcase at a height of 2 m 
Step-by-step explanation:
The gravitational potential energy (GPE) of an object is given by:

where
m is the mass
g is the gravitational acceleration
h is the heigth above the ground
We can use the formula to calculate the GPE of each object:
A.A 30 kg suitcase at a height of 1.5 m

B.A 20 kg suitcase at a height of 2 m

C.A 30 kg suitcase at a height of 2 m 

D.A 20 kg suitcase at a height of 1.5 m.

So, we see that the object which has the most GPE is C.