What 2 adaptions do plants have to conserve water?

Crossing over is a method of (blank)?

The greenhouse effect a. something that has occurred for millions of years b. an unnatural phenomenon caused by humans that maintains earths temperature range. c. the results of the differences in the angle of the suns rays d. an unnatural phenomenon that causes heat energy to be radiated back into the atmosphere

Can yall plz me on this question im having a hard time think about it