Only one task may hold the mutex at a time, and only this task can unlock the mutex.

一次只能有一个任务持有互斥锁，并且只有这个任务可以解锁互斥锁。

youdao

They are interesting for the fact that they are very plain and undecorated for the time, with only one plain central panel at the back and no armrests.

很有趣的是，当时它们很普通，没有装饰，只是后面有一个简单的中央面板，没有扶手。

youdao

My mind could only assimilate one impossibility at a time.

我的头脑一次只能吸纳一件不可能的事情。

《柯林斯英汉双解大词典》

For a time he was one of only three doctors,and the only surgeon, at a huge hospital in Kinshasa.

VOA: special.2009.02.23

Water Calvin he was the only one..magnificent Water Calvin would like to have me at his home all the time.

他就是这样一个人。。。伟大的,他总是让我去他家。

普林斯顿公开课 - 人性课程节选

It's this extraordinary insight that he gives us: we can only read one word at a time, we can only read one line at a time.

这是他告诉我们的非凡的洞察：,我们一次只能读一个词，或是一行。

耶鲁公开课 - 弥尔顿课程节选

But his colleagues have warned Mr Ashdown that he can now take only one step at a time, and even then only after he has consulted first with his front bench.

ECONOMIST: Why Paddy will miss Peter most

Now, the United States has only one government and one president at a time.

NPR: Can The Global Crisis Wait For A New President?

There's only one president at a time, occupying the toughest job in the world.

CNN: Give Obama a break