1.Can I ask____question?
A.a B.an C.two D.x
2.The fisherman was making____fishing net.
A.x B.a C.an D.two
3.I'm eating____food I bought downstairs.
A.a B.an C.the D. two
4.Allen pulled out the nails___a pair of pliers.
A.at B.on C.by D.with
5.She___to the washroom.
A.a B.went C.going D.was go

1.A
意思是:我能问你一个问题么?
泛指,所以用a
2.B
意思是:那个渔夫正在做一个鱼网.
一个,所以用a
3.C
意思是:我正在吃我刚才在楼下买的食物.
特指,而且食物不可数,所以用the
4.D
意思是:Allen用一个老虎钳把钉子给拿出来了.
with是"用"的意思.
5.B
意思是:她去厕所了.(表示过去)
D项应该是was doing,其他选项也可以排除,所以只能选B