He let a week ( ) by before ( ) the letter.选A对的吗?求教,
问题描述：
He let a week ( ) by before ( ) the letter.选A对的吗?求教,
A.to go; answer B.go; answering C.to go; to answer D.go; to answer
答
B
let是使役动词,后面的宾补用动词原形,排除A和C.before是介词,其宾语用动名词,不定式不能作介词的宾语,排除D.