21.Which of the following is a monotreme? A. Lizard B. Kangaroo C. Oppossum D. Duck-billed platypus E. Dog 22.How many sperm cells are produced for every one primary spermatocyte? A. 2 B. 4 C. 8 D. 12 23.Which part of the sperm cell contains enzymes to help the sperm digest a pathway into the egg? A. Tail B. Centriole C. Body D. Head E. Acrosome 24.In humans, how many ova are produced from one primary oocyte? A. 1 B. 2 C. 4 D. 8 25.The secondary oocyte does not complete the second meiotic division until: A. ovulation B. puberty C. fertilization D. birth  Â