Final answer:
A monkey's gamete cells have 10 chromosomes, half the number of chromosomes found in the body cells.
Step-by-step explanation:
In a monkey's body cells, there are 20 chromosomes. These cells are known as somatic cells and are diploid, meaning they have a complete set of chromosomes. On the other hand, a monkey's gametes cells, which are its reproductive cells, are haploid and have half the number of chromosomes compared to somatic cells. Therefore, the number of chromosomes in a monkey's gametes cell would be 10 chromosomes.