The living things die because there is no ______ in the river or sea.

A．Small animals have less skin for their body weight than large ones.
B．The humming-bird lives faster than any other warm blooded animals.
C．There is no limit to how large a warm blooded animal can be.
D．The humming-bird is the smallest of the warm blooded animals.

A．have more skin for their weight
B．bum fuel faster than big ones
C．replace lost heat faster
D．keep a high body temperature