Please answer the one that is wrong

Use composition to determine if (x) or h(x) is the inverse of f(x) for the limited domain x2-1.

The weight of a radioactive isotope was 96 grams at the start of an experiment. after one hour, the weight of the isotope was half of its initial weight. after two hours, the weight of the isotope was half of its weight the previous hour. if this pattern continues, which of the following graphs represents the weight of the radioactive isotope over time? a. graph w b. graph x c. graph y d. graph z

Me i'm timed right now! a. (0,-5)b. (0,-3)c. (0,3) d. (0,5)