已知相异直线a，b和不重合平面α，β，则a∥b的一个充分条件是（　　）

A．a∥α，b∥α

B．a∥α，b∥β，α∥β

C．a⊥α，b⊥β，α∥β

D．a⊥β，a⊥α，b∥β

One of the requirements for a fire is that the material______to its burning temperature.

A．is heated

B．will be heated

C．be heated

D．would be heated