三道英语专四题目1.———you---------further problems with your printer,

三道英语专四题目
1.———you---------further problems with your printer,contact your dealer for advice.
为什么要用should,have.而不能用if,had
2why are you staring?-i anve never seen------tree before
为什么用that kind of 而不能用such
3-------dull he may be,he is certainly a very successful top executive
为什么要用However 不能用although