Q: Q: Parasitic leeches feed off of what?   A:
A: blood

Q: Q: What do sharks use to secrete salt to assist in osmoregulation?   A:
A: rectal gland

Q: Q: What system lets flatworms maintain a proper balance of water and salts?   A:
A: excretory

Q: Q: Passive immunity arises from the transfer of what to an individual, without requiring them to mount their own active immune response?   A:

A: antibodies