Most sperm cells die in the vagina when entering the female's body because
A) the sperm cannot pass through the mucus.
B) the female's reproductive tract is protected by digestive enzymes.
C) of the low pH of the vagina.
D) the sperm cells have not yet been activated to swim.
E) macrophages from the female's immune system destroy all nonself cells.
C
You might also like to view...
In osmosis
A. water moves from extracellular to intracellular compartments. B. water moves from a region of high water concentration to a region of low water concentration. C. solutes move from a region of low water concentration to a region of high water concentration. D. solutes move from a region of high solute concentration to a region of low solute concentration. E. plasma membranes must be impermeable to water.
Most innate immune responses rely on
A. recognition of specific antigens. B. pathogens being engulfed and destroyed. C. plasma cells to secrete antibodies. D. IgM antibodies. E. clonal selection to replicate specific lymphocytes.
Even though the caudal fin of sharks tends to direct the fish downward when swimming (due to slight downward force generated by the heterocercal tail) the shark still manages to swim at a fairly consistent depth. Explain how can this be so
What will be an ideal response?
The encysted larva of the beef tapeworm is called a
A) redia. B) cercaria. C) cysticercus. D) metacercaria. E) proglottid.