The astronauts have to lie ________ the floor of the spaceship to fight against the great pressure during the flight.

A．in

B．beyond

C．against

D．at

煤在炭化室内加热到20-200℃时称为（）阶段。

A．干燥预热

B．分解出胶质体

C．半焦转为焦炭

D．热解