Can someone explain to me why a is the answer? i’m a bit confused.

Select the correct answer from each drop-down menu. in an experiment, dr. travis examined the effects of calcium intake on osteoporosis, a condition that causes an increased risk of bone fractures. the amount of calcium is variable. the risk of bone fractures .

For this question look at the hydropic diagram water that is heated by the sun evaporates. select the number that represents it.

What are the three types of counseling established by marine corps policy?