单项选择题
A．It is secreted by the kidneys into the bloodstream. B．It is hormone that prepares the body for emergencies. C．It is the only useful hormone produced in the body. D．It is essential to sustain lif
A．and B．but C．yet D．so
A．a scientist as well as a naturalist B．a naturalist but not a scientist C．no more than a born naturalist D．first of all a scientist