The boy never lets his friends（ ）when they need his help.
A、
in
B、
down
C、
off
D、
out
【正确答案】：B
【题目解析】：
A.let sb. in：让某人进来；B.let sb. down：让某人失望；C.let sb. off：让某人下车；D.let sb. out：使某人解脱，根据意思“当别人需要他的帮助时”，他应该是不让别人失望，选B。句意：当朋友需要他的帮助时，他从不让他们失望。
The boy never lets his friends（ ）when they need his help.
The boy never lets his friends（ ）when they need his help.
in
down
off
out
A.let sb. in：让某人进来；B.let sb. down：让某人失望；C.let sb. off：让某人下车；D.let sb. out：使某人解脱，根据意思“当别人需要他的帮助时”，他应该是不让别人失望，选B。句意：当朋友需要他的帮助时，他从不让他们失望。