单项选择题
A. must check B. should check C. must have checked D. should have checked
This device looks simple enough, but () it is very comp...
单项选择题This device looks simple enough, but () it is very complicated.
A. on the surface B. in appearance C. as a rule D. in fact go
() they have the opportunity, many Americans take their...
单项选择题() they have the opportunity, many Americans take their vacations away from home.
A. However B. Wherever C. Whatever D. Whenever
