Mr. Fotheringay struggled to get to his feet ______ vain and rem

Mr. Fotheringay struggled to get to his feet ______ vain and remained on all fours ______ on.
A、at,holding
B、in,holding
C、at,held
D、in,held
【正确答案】：B
【题目解析】：本题考查in vain和动名词做伴随状语。at vain无意义，故可排除A和C。hold on：坚持，继续前行。因为句中主语和hold是主动关系，故排除D。答案为B。