The boy felt very _______ and fell _______ as soon as he lay on the bed.

A．sleepy; sleepy

B．asleep; asleep

C．sleepy; asleep

D．asleep; sleepy

通气管高出屋面不得小于（）m，且应大于最大积雪厚度，通气管顶端应装设风帽或网罩。