单项选择题
A．Make sure there is no misunderstanding. B．Try to persuade by giving various reasons. C．Repeat the same reasons. D．Listen carefully and patiently to the other party.
A．When it is breeding. B．When it feels threatened by humans in its territory. C．When its offspring is threatened. D．When it is suffering from illness.
A．Its chemical elements must be studied. B．Its temperature must be lowered. C．Big spaceships must be built. D．Its atmosphere must be changed.