The theory is that the water is acting as a lubricant.原理是水起到了潤(rùn)滑的作用

act as:擔(dān)任, 充當(dāng)

He was appointed to act as the executor.

他被指定為遺囑執(zhí)行人。

Maybe I can act as a messenger for you.

也許我能給你當(dāng)信差。

To the naked eye, glaciers don't appear to move at all.肉眼看來(lái)冰川好像巋然不動(dòng)

appear to:看來(lái)像是, 看來(lái)似乎

They appear to be able to handle the problem.

他們似乎可以處理這個(gè)問(wèn)題。

The students appear to be completely out of hand.

學(xué)生們似乎已完全無(wú)法控制了。

at all:完全, 根本

It's not at all that bad.

這根本沒(méi)有那么壞。

Whatever is worth doing at all is worth doing well.

任何值得做的事就值得做好。