Answer:
Sperm cell: 23
Egg cell : 23
White blood cell : 46
WHY?
Sperm cell and egg cell are gametes. They are the product of meiosis (chromosome reduction nuclear division). This ensures that during fertilisation, the Zygote formed would have 2 sets of chromosomes to form a genetically viable offspring. Therefore, gametes needs to be haploid with 23 chromosomes.
For a white blood cell, it is a somatic cell. Somatic cells undergo mitosis. (Nuclear division with no reduction in chromosomes) This ensures that cells are genetically identical to each other. Therefore, White blood cells needs to have 2 sets of chromosomes to ensure it's viability. Thus, it has 46 chromosomes.