When she was a child, she used to help her mother on the small farm_____ they lived.    [ ]

A. in which    

B. on that      

C. there        

D. where

在我国，家庭电路的电压是_______V，每个用户之间的电路连接方式是_______联；今年高考，湛江市首次使用金属探测仪防止考生作弊，金属是______（填“导体”或“绝缘体”）．