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题库 / Prep2007E2-SC-80
Although at one time children's programming had been limited to a few hours a week, now, however, there are at least four cable networks that dedicate themselves entirely to shows produced specifically for children.
Although at one time children's programming had been limited to a few hours a week, now, however, there are at least four cable networks that dedicate themselves
With children's programming having been limited at one time to a few hours a week, now at least four cable networks have dedicated themselves
Once limited to a few hours a week, there are now at least four cable networks with children's programming that dedicate themselves
Children's programming was once limited to a few hours a week, but now there are at least four cable networks dedicated
While children's programming had once been limited to a few hours a week, at least four cable networks are now dedicated
dedicate 主动语态时，主语是人，sb dedicate oneself to do ,表示某人献身于某事业；dedicated被动语态时，主语是物体，sth is dedicated to sth,表示某物被专用于xxx
choice e is incorrect because of its inappropriate use of the past perfect. if you're going to say kids' programming had once been limited to ..., then you must reference a second past event. this sentence doesn't do that: the second event referenced is in the present (specifically, 'now').
e, had been时态不对，转折意味but更好
E，had错误。
D，there are表示虽然之前孩子们的节目被限制在一周几小时，但现在至少有四个有线电视网络专门为儿童制作节目。
d和e重要的是转折意味的不同
dedicate是主动语态，E的话应该说are dedicating 或者直接用dedicate
While引导的主从句，谓语在时间上要一致，没有先后。
（A）wrong，2 reasons
1. Dedicate oneself to blablabla_>subject should be a person or a life.
Sth is dedicated to->right. Subject should be Thing, generallly.
2. Had+p.p. Wrong usage here.
为什么不选E？
had been时态不对
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