Answer:
Luster
Step-by-step explanation:
luster is the only answer that has to do with light. Luster is measured by the way a mineral reflects light.
Cleavage has to do with breaking minerals apart along certain fracture lines. Cleavage is not the answer.
Hardness is a test where one mineral is used to scratch another. The one that does the scratching is harder than the one that is scratched.