The film ________ a novel ___________ by Robert James Waller called Bridges of Madison County.

A is based on; written         B base on; writing

C base on; written            D is based on; writing

220kV的耐张绝缘子串应预留的零值绝缘子片数为( )。

A．0；
B．1；
C．2；
D．3。