d. all of the above
Work Step by Step
Meiosis is necessary for sexual reproduction because it halves the chromosome number; this process forms the sex cells called gametes from germ cells, the only cells in the body capable of meiosis. Because each gamete contains only half the number of chromosomes as a regular body cell, something has to be done to return the chromosome number to its original diploid condition. By uniting male and female gametes to form a new cell, fertilization occurs, and the chromosome number is restored.