问题

production of television commercialsmust be professional ________ they aim at promoting good service, or publiceducation.
A:when
B:no matter
C:if
D:whether
B:no matter
C:if
D:whether
正确答案是:
同类题型
Only when ______ the data again ______ that there was a mistake. [ ]
Jim often plays ______ basketball after school and plays ________ guitar in the evening.
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