难以保存

difficult task───艰巨的任务

difficult time───困难时期

difficult issue───难题

difficult process───艰难的过程

difficult terrain───困难地形

difficult opponent───难对付的对手

difficult position───困境

difficult birth───难产

difficult match───困难的比赛

also difficult to keep program versions.───保存程序的版本也很困难。

With eleven thousand employees, it's very difficult to keep track of them all.───有11000名员工，很难了解他们所有人的动向。

Some teachers find it difficult to keep their classes in order.───有些教师觉得难以维持课堂秩序。

He told me that this drought has taught him a hard lesson: it is too difficult to keep animals.───他告诉我干旱给了他一个沉痛的教训：饲养动物太困难了。

In a fierce argument, it is often difficult to keep hold of one's main point.───在激烈的辩论中，一个人很难把握住自己的主要论点，使之不走样。

Understand that I am growing up and changing very fast. It must be very difficult to keep peace with me, but please try.───你要明白，我正在长大，因而多变——和我友好相处，一定是件难事吧。

"Certainly it would be really difficult to keep the player, but we believe in this, " he said.───当然想把他留下很困难，但我们相信我们可以办到。

However, it is always difficult to keep track of where that testing is in terms of status and coverage.───但是，根据状态和覆盖率总是很难追踪该测试在哪里。

It is possible to restrict deliberate dumping in marine sanctuaries , but difficult to keep out whatever comes from adjacent land and sea.───人们可以采取措施限制向海洋保护区倾倒废弃物，但是很难控制由附近的陆地或者水域带来的任何有害物质。

It can be difficult to keep children occupied during the long summer holidays.

With eleven thousand employees, it's very difficult to keep track of them all.

It's difficult to keep track of all the new discoveries in genetics.

I was finding it increasingly difficult to keep my temper.

I found it very difficult to keep a straight face .

The procedures are continually revised?it is very difficult to keep up with the latest version.

It is difficult to keep up with the rapid pace of change.

It is difficult to keep one's balance on an icy pavement.

It's difficult to keep your self-respect when you have been unemployed for a long time.