问题
选择题
. The production of television commercials must be professional ________ they aim at promoting good service, or public education.
A．when
B．no matter
C．if
D．whether
答案
答案：D
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. The production of television commercials must be professional ________ they aim at promoting good service, or public education.
A．when
B．no matter
C．if
D．whether
答案：D