If you try to pass （） the problems, it would be impossible for you to make any progress in this field.

单项选择题Once he set his mind to（）something, he would not give up easily.

A．do
B．doing
C．be doing
D．having done

单项选择题Were it not for your help, I （） in trouble now.

A．was
B．were
C．had been
D．would be