Professor James will give us a lecture on the Western culture, but when and where yet.
A. hasn’t been decided
B. haven’t decided
C. isn’t being decided
D. aren’t decided
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(答案→)A. hasn’t been decided
B. haven’t decided
C. isn’t being decided
D. aren’t decided
解析：考查时态及主谓一致。主语when and where作主语，谓语动词用单数，根据yet可知为现在完成时，选A。