单项选择题
Sharks can stop themselves from sinking because()
A．their dorsal fins are very valuable B．they have a swim bladder C．they have fins for swimming D．they have skeletons made of cartilage
单项选择题 The housewives learned about the offer of free goods ()
单项选择题 Sharks are()
单项选择题 Mrs. Edwards' husband tried to ()
