请问老师while在这里是什么用法？Its Intelligent Transport System tells drivers when roads are crowded,
while changing traffic lights and planning alternative routes that drivers can
follow.
...e
had trouble getting enough people to sign up. 我们没能说服足够多的人报名参加。We
will not have the picnic unless more people sign up. 除非有更多的人报名参加，否则我们就不举行野餐了。There
was an attempt to sign up more men for the police force, but not many ...
...ully. 这里一上来就使用过去完成时，是因为参照后面一句的过去时间 I began
to...对吗？2)
The examiner must have been pleased with my performance - 这里既能理解成作者在当时（在过去）对更早的过去的推测，也能理解成作者在写这篇文章的时...
前面有网友的一个问题中涉及了 wish for sb to do sth 句型，但我记得有个句型是 wish sb to do sth，那 wish sb to do sth与wish for sb to do sth这两个句型一个有介词 for，一个没有介词 for，它们有何区别呢？比如下面两句，它们的区别是什么...
...法书上讲，Lu Xun (鲁迅)
has visited Guangzhou. 这个句子是错误的，因为“鲁迅早已不在人世”。但是改为被动句Guangzhou
has been visited by Lu Xun (鲁迅).
这个句子就是正确的了。书上给出的理由原话是，“一个句子的谓语动词用什么时态...
先看两个句子：I don’t want to spend any more money than necessary.I think it’s bigger than is necessary.我的疑问：1. 第一句用 than necessary, 第二句用 than is necessary, 两者有何区别？2. 这是省略吗？是省略了什么成分？
[A]TV industry had withdrawn to its domestic market[C]machine-tool industry had collapsed after suicidal actions这两个句子不懂，A中的withdrawn的含义，如何理解呢？C中的collapsed after suicidal actions如何理解？