感冒时常感到呼吸不畅通,这主要是因为( )
A:气管分泌的粘液增多
B:喉结肿胀,喉腔变小
C:参与气体交换的肺泡数减少
D:鼻黏膜充血肿胀
He always sits the classroom, because he is short(矮).