She asked if any of the passengers ___ anything about machines.A.masteredB.knewC.understoodD.learned这道题的答案是B,可我认为B、C都对了.为什么选B不选C?

She asked if any of the passengers ___ anything about machines.A.masteredB.knewC.understoodD.learned这道题的答案是B,可我认为B、C都对了.为什么选B不选C?
She asked if any of the passengers ___ anything about machines.
A.mastered
B.knew
C.understood
D.learned
这道题的答案是B,可我认为B、C都对了.为什么选B不选C?

She asked if any of the passengers ___ anything about machines.A.masteredB.knewC.understoodD.learned这道题的答案是B,可我认为B、C都对了.为什么选B不选C?
know sth about... 固定结构, "了解,知道,听说过"某某东东
understand sth about 没有这样的结构