Sometimes they may play to passers-by in the street or subway so that they can earn some money for themselves or to pay for their instruments.
A. certain
B. extra
C. various
D. unusual
网友回答
A. certain
(答案→)B. extra
C. various
D. unusual
解析：考查词义辨析。certain 一定的，extra 额外的，various 各种各样的，unusual 不寻常的，句意：有时候他们可能在大街上或地铁给过路人弹奏，因此他们能挣一些额外的钱为他们自己或付他们的乐器。故选B。