Final answer:
The sex of most ants and bees is determined by their chromosomal number (haplodiploidy) where females are diploid and males are haploid. The correct option is D.
Step-by-step explanation:
In most ants and bees, sex is determined by the number of chromosomes an individual has, a system known as haplodiploidy. This is different from the Z-W and X-Y systems used in other animals. Female ants and bees are diploid, meaning they have two sets of chromosomes, which they receive from both the mother and the father.
Males, on the other hand, are haploid, developing from unfertilized eggs and thus having only one set of chromosomes that they inherit from their mother. This means that by the number of chromosomes is the correct answer to how sex is determined in most ants and bees.
Therefore, the correct option is D.