Problems of long _______ should be handled with great care.

Problems of long _______ should be handled with great care.
A、time
B、period
C、standing
D、stand
【正确答案】：C
【题目解析】：time时间；period期间；stand站台；problems of long standing长期存在的问题
句意：长期存在的问题要小心处理。