He tried to listen carefully but still couldn't（ ）what they are

He tried to listen carefully but still couldn't（ ）what they are talking about.
A、make over
B、make out
C、make upon
D、make up
【正确答案】：B
【题目解析】：A.make over：转让，移交；B.make out：勉强看/听/辨认出来； C.make upon不是固定词组；D.make up：虚构，化妆，组成。选B。句意：他试着仔细听，但还是没能听清他们在谈什么。