Final answer:
A trisomic body cell in an animal with 20 chromosomes in its gametes would have 41 chromosomes in total, given the extra chromosome in addition to the normal diploid number.
Step-by-step explanation:
In biology, when an animal's gametes contain 20 chromosomes, typically, this means that its body cells (or somatic cells) contain twice that number in a diploid state, which would be 40 chromosomes. A trisomic body cell will have one additional chromosome than the normal diploid number.
Therefore, a trisomic body cell in this particular animal would contain 41 chromosomes, which correlates to option b) 21 more chromosomes in addition to the 20 pairs present in the diploid state.