A.check
B.chemist
C.chicken
D.children

A．To test the relationship between daylight and a disease of the glands common to birds.
B．To test the relationship between daylight and migration.
C．To test the relationship between migration and temperature.
D．To test the relationship between daylight and changes in the season.

A．The sloth does not eat any meat
B．For most of its time, the sloth remains motionless on the ground
C．To some extent, the sloth is protected by the moss growing on its body
D．The sloth has a brown fur of its own