timing的动词原形是什么

例句：

1、The heating is on a time switch.

暖气靠定时开关自动供热。

2、We do not have any more information at the present time.

目前我们没有进一步的消息。

3、This will be a problem for some time to come.

这将是未来一段时期里的一个问题。

4、We'll be there in less than no time.

我们马上就到。