Answers for number nine, 10, and 11

A  the chromosomes from another parent cell were introduced

Explanation: A child is created when the male sex cell joins the female cell. If the male and female sex cells had the standard number of chromosomes, as is found in body cells then the zygote (baby) would have double that number of chromosomes. The number of chromosomes would keep doubling every generation. To avoid this doubling the parent's body cells split by miosis which halves the number of chromosomes and so when the sex cells join the total number of chromosomes is the same as that found in the parent's body cells.