If you want to be certain of getting a ticket, book now.

要想有把握买到票，现在就得预订。

They'll have to give up completely on certain of their studies.

他们将不得不完全放弃某些课程。

Certain of those present were unwilling to discuss the matter further.

某些在场的人不愿意进一步讨论这个问题。

Time has winnowed out certain of the essays as superior.

历经岁月的淘洗，有些文章成为经典。

You'll have to leave soon to make certain of getting there on time.

你得快点出发，好确保准时到达那里。