Iwant all this questions answer plz give me

Why is it important to reduce the number of chromosomes in half when forming gametes for sexual reproduction?

During binary fission, what events must occur before the cell splits into two new cells?

Which of the following statements is true about the relationship between genetic variation and natural selection? a. genetic variation must be present in a population before natural selection can act on it. b. genetic variation arises in a population as a result of natural selection. c. natural selection can act on a population whether there is genetic variation within the population or not. d. after natural selection acts on a population, the amount of genetic variation in the population always increases.