The girl was very sad, and she seemed _____ the fact that she didn’t pass the exam.[ ]

A. telling                            

B. having told

C. to be told                    

D. to have been told  

如图D-12分压器电路中，在开关S闭合的情况下，滑动触头在位置a时输出电压Uex是多少伏？在位置b时输出电压Uex是多少伏？在中点c时输出电压Uex是多少伏？