Small sailboats can easily turn over in the water ________.

if not managed carefully

if are not managed carefully

unless not managed carefully

unless are not managed carefully

The old rules have to be          because they only applied to the circumstances that existed when they were made a hundred years ago.

developed

established

observed

revised

考查动词的辨析。句意：老的规则需要被修改因为它们只适合一百年制定时的状况。A.develop发展；培养；B.establish建立；C.observe观察；D.revise修改，由because they only applied to 可知它只适用于以前，需要修改。故选D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。

The programme can't be             him because it is beyond his ability.

charged with

in charge of

taken charge of

in the charge of

考查固定短语辨析。句意：这个项目不可能由他负责，因为它超出了他的能力。A. charged with控告；B. in charge of负责，主管；C. taken charge of 接管，负责；D. in the charge of 由......负责。根据because it is beyond his ability及空格后him可知用in the charge of 符合题意。故选D项。