A．they tend to take in less vitamin D in that season.
B．they do less exercise and become weaker than usual.
C．they need to eat much more greasy food to keep warm.
D．they get less sun to convert cholesterol into vitamin

A．the world’s earthquake laboratories were not effective in detecting seismic "pre-shocks".
B．seismic signaling was the major communication form of many animal species.
C．those animal species can feel and understand all kinds of vibrations.
D．all storage animal behaviors can be explained by extra-sensory perception.