The signal (for) a race to start is often the firi

问题补充：

The signal (for) a race to start is often the firing of a gun.括号里的for能否改为of?

答案：

这是约定俗成的用法

======以下答案可供参考======

供参考答案1:

不能注意后面的to start

要改的话应该是：the signal of a races starting is often the firing of a gun.

供参考答案2:

可以，【signal for】和【signal of】基本可互换，区别不大

翻译：一场赛跑的信号通常是鸣枪。

祝你学习进步，更上一层楼！

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供参考答案3:

不行。固定用法。