单选题：_______a mobile phone can _______you ring you want to talk w..

For a moment nothing happened then _____all shouting together. [ ]A. voices had come B. came voices C. voices would come D. did voices come

John opened the door. There ________ he had never seen before.[ ]A. a girl did standB. a girl stoodC. did a girl standD. stood a girl

Only when the villagers were faced with water shortage___ how serious the problem of water pollution was．A．did they realizeB．will they realizeC．they did realizeD．were they realized

_____ that it was sold out when it came out. [ ]A. So was her successful book B. So successful was her book C. So her book was successful D. So successful her book was

This is an illness that can result in total blindness if_______. A．to leave untreatingB．left untreatedC．leaving untreatingD．is left untreated