zhonglc2020 wrote:What about the option C? What are those reasons behind?
(1) We don't know much clearly what "it" refers to or something else?
(2) The above said though-because problem?
I think the main problem is the "it".
Really, an "it" (as a subject) in one clause usually refers to the noun (subject) in the other clause.
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So "it" should refer to "the mountain climbers" - which does not make sense (this is a plural noun). The only thing which is mentioned which could be an "it" is Mount Qomolangma.
To follow this rule, Mount Qomolangma would have to be used as the subject of the second clause:
Great difficulty as it was, Mount Qomolangma was climbed in the end.However, this does not work well either - because the difficulty was
the climbing, not the mountain.
A mountain just sits there doing nothing, it's not a difficulty.
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The only way I can see to make it work is to make "the climbing" into a subject.
Great difficulty as it was, the climbing of Mount Qomolangma was achieved in the end.Not the best-sounding sentence, but it seems OK.