What do sexual reproduction, mutation, and crossing-over generate in a population

The correct answer is genetic diversity.

Explanation:

During sexual reproduction, two different gametes from two different parents combine to form offspring which is genetically different from their parents. Mutation in the genetic material of germ cell passes to the offspring during fertilization in sexual reproduction which causes genetic diversity or variation.

Crossing- over also helps in generating the genetic diversity because during crossing over genetic material is exchanged between homologous chromosome which changes DNA sequence in chromosome causing variation in gametes.

Therefore sexual reproduction, mutation, and crossing over generate genetic diversity in a population.

because of

desert perennials often survive by remaining dormant during dry periods of the year, then springing to life when water becomes available. most annual desert plants germinate only after heavy seasonal rain, then complete their reproductive cycle very quickly.