Although the quality of these goods is ____ usual standard, we a

Although the quality of these goods is ____ usual standard, we are prepared to accept the goods if you will reduce the price, say, by 20%.
A、not in line with
B、not conform to
C、not up to
D、not in conformity to
【正确答案】：C
【题目解析】：be not up to不能胜任