Though ____ the dangers of smoking to their health, smokers still find it hard to give up smoking.

aware of

are aware of

be aware of

考查状语从句的省略：句意：虽然很多经常吸烟的人已经意识到抽烟对他们健康造成了很严重的后果，但是他们仍然发现很难戒烟。Though引导的让步状语从句是省略句，完整的句子是：though smokers are aware of the dangers of smoking to their health。当主从句的主语一致的时候，可以省略从句的主语和be动词，选B

The information tells me that the way of education in Canada is quite different from          in China.

one

it

that 

those

考察代词。句意：这条信息告诉我们在加拿大的教育方式和在中国的教育方式很不一样。前后比较的是教育方式，用that 指代the+名词。A. one 是泛指一个，B.it 指的是同一个东西，D. those指代the +名词复数。故选C项。

Let's learn to use the problem we are facing         a stepping-stone to future success.

to

for

as

by

考查介词词义辨析。句意：让我们学会把我们所面对的问题作为通向未来成功的手段来利用。A.to朝，对 ；B.for 为了，对于；C.as 作为；D.by通过，凭借。根据句意可知，此处“作为”符合语境。故选C项。