完成句子

小题1:The twins look __________in some ways, and they look different in some ways.(相同)

小题2:Most students go to school __________ in this city.(步行)

小题3:My grandpa is pretty healthy because he __________every day.(exercise)

小题4:I want to __________ this summer holiday.(观光)

小题5:He can’t go to my party, because he __________ look after his sick mother.(不得不)

若要降低某洁净室室内含尘浓度，下列处理方法综合效果最好的是( )。

A．提高出风口上过滤器的效率

B．提高回风口上过滤器的效率

C．减低室内建筑壁面的发尘量

D．提高新风过滤器的效率