Which choice can be classified as a pure substance? A. homogeneous mixture
B. compound
C. heterogeneous mixture
D. solution

compound

Explanation:

I hope it's helpful for you

I'm having some difficulty seeing the diagram clearly.but the question says there's a net inward force on the object.so we know right away,  from newton's 2nd law of motion, thatthat baby is accelerating.  it doesn't even matter which way thenet force is pointing.  if there's any net force, then either theobject's speed or else its direction must be changing.

D. the index of refraction of the second medium is lower.