Step 1: Variable Quantities
[Ref. Fig.]
Here speed is changing at every instant, and height is also changing during motion.
Kinetic Energy =12mv2
Potential Energy =mgh
v and h are changing so kinetic and potential energy will change.
Step 2: Constant Quantities
In x direction there is no acceleration (ax) so horizontal component of velocity will not change (constant).
In y direction acceleration is constant i.e. g. Therefore total acceleration is also constant.
Hence option C is correct.