XDF蓝皮中册P43T5???

Because the enemy's new ship is the quietest and it is therefore the most elusive submarine it is being increasingly viewed by the military as a threat to security.

A), and it is therefore the most elusive submarine it is being increasingly viewed

B) it is therefore the most elusive of submarines, and it has increased the view

C) and therefore the most elusive submarine, it is being increasingly viewed

D) and therefore it is the most elusive submarine, there is an increasing viewed

E) therefore being the most elusive submarine, it is  increasingly viewed

Why the answer is C?

首先觉得前面应该是and therefore the most elusive submarine

原因是，主语相同，所以it is必须省略，and不能省，他表并列，therefore,副词表明前后的因果关系，也不能省

E觉得没必要用being因为前后是并列的

这样就可以得到C了

至于后面有现在进行时，觉得表达连续的过程，increasingly表达的是个连续的正在进行的过程

个人看法，我刚开始看SC的菜鸟，说得不对请指正