{A} INCORRECT; we need "that" before stargazers..
{B} INCORRECT; it is trying to connect both the invents.. also "more than ever before clearly visible" is awkward
{C}
{D} INCORRECT; we need "than"; also "while" is changing the meaning
{E} INCORRECT; using "so" doesn't show that engineers are claiming

{C}?

qwerty12321 wrote:A new telescope scheduled for completion in 2012 is greatly anticipated by astronomy enthusiasts because engineers claim that the machine will allow the night sky to be observed more clearly than never before and stargazers using the telescope will be able to see constellations that cannot presently be observed- almost perfectly.

(A) observed more clearly than never before and
(B) more than ever before clearly visible as
(C) more clearly observed than ever before and that
(D) more clearly visible as never before while
(E) clearly observed more than ever before so

Hi qwerty12321,

There are a couple of answers to this question which can be eliminated right away (which is helpful for quickly moving through GMAT questions). Both answer A and D incorrectly use the word "never" in the phrase "than never before" - it should be "than ever before." Eliminate A and D.

Answer B is both awkward and incorrect, in that it suggests that the new telescope will make the night sky more often visible, rather than more visible, which is contrary to the intended meaning of the sentence. Eliminate B.

Answer E is also awkward and incorrect, for two reasons. Like answer B, it suggests that the new telescope will make the night sky more often visible, rather than more visible, which is contrary to the intended meaning of the sentence. It also incorrectly uses the word "so" at the end of the clause. "So" is a word that is usually used to show extremes, for example "This pancake has so much syrup on it!" and "Ted so rarely comes to class on time." Eliminate E.

Answer C is correct!