桥涵顶进施工，线路加固方案采用较多的有（）。
A、横梁加固法
B、横梁加固法纵
C、扣轨方案
D、便梁法
参考答案：C
It is believed that a new kind of drug ______ by the scientists and they are hopeful that they
will succeed in a couple of months. [ ]
A. has been developed
B. is being developed
C. is developing
D. has developed
