[单项选择]对于血运和呼吸运动均有推动作用的是( )
A. 心气
B. 宗气
C. 脾气
D. 卫气
E. 营气

Researchers have found that migrating animals use a variety of inner compasses to help them navigate. Some (1) by the position of the Sun. Others navigate by the stars. Some use the Sun as (2) guide during the day, and then (3) to star navigation by night. One study shows that the homing pigeon uses the Earth’s magnetic fields as a guide (4) finding its way home, and there are indications that various other animals, from insects to mollusks (软体动物), can also make (5) of magnetic compasses. (6) is of course very useful for a migrating bird to be able to switch to magnetic compass when clouds cover the sun; (7) it Would just have to land and wait for the Sun to come out again. (8) with the Sun or stars to steer by, the problems of navigation are more complicated (9) they might seem at first. For example, a worker honeybee (10) has found a rich source of nectar and pollen flies rapidly home to the hive to
A. their
B. its
C. one’s
D. theirs