—Did you have any problems in London ?

—Yes, I have trouble ______ Chinese food like noodles.

A．finding

B．found

C．find

D．to find

一台螺杆式低压空压机，运行中发现管线压力与机内压力的压差大于1Bar（从空压机面板上可直观看出两块的压差），请试述其原因。