He studied as hard as he could _____ to enter a good college.

A．hope

B．to hope

C．hoping

D．hoped

可确诊食道阻塞的方法是（）

A.吞咽障碍

B.食道视诊或触诊

C.胃管探针

D.X光检查有异物阴影

E.触摸