One of the necessary conditions for using the method of graph multiplication is ( ) .

A、thebendingmomentdiagramisastraightlineunderunitload;
B、thestructurecanbedividedintostraightmemberswithuniformsection;
C、theflexuralrigidityEIofallmembersisaconstantandequal;
D、astructuremustbeastaticallydeterminatestructure