请根据括号中的中文提示、英文释义或句意，写出句中所缺单词，使句子通顺。

小题1:Tom is __________ (缺席) from class today. His mum is ill, he has to look after her at home.

小题2:We should pay attention to ________ (grow and improve) a good habit of study.

小题3:I received his invitation yesterday, but I didn’t _________ it because I had something more important to do.

小题4:Our earth is becoming dirtier and dirtier. We should try our best to reduce the __________(the state of being dirty)   

小题5:He will write to me as soon as he __________(到达) Paris.

高层仓库应设置()楼梯间。

A.防爆

B.防火

C.封闭

D.泄压