The concept is like that the survey has been already completed. so we cant use ing form.

Great question, GMATJeet - I know and love this sentence and I like the way you phrased your question.

In addition to jainnikhil's concerns with C, I'd add this, as well...

"retiring" is parallel to "facing" if they're both used as gerunds (-ing forms of a verb used as a noun...don't worry about the term "gerund" as long as you see that both could be used as nouns in that form). But since "facing" is a verb, how do we know, in C, that it's not supposed to be parallel to "have elected", another verb opposite the decision point if "instead of"? That's at least a potential point of confusing - and with the infinitive "to retire" after "elected" in E, there's no such confusion...the infinitive sets that clause away from "have elected".

So in C, you the X instead of Y construction could be:

they have elected X instead of facing Y
or
they have elected X instead of Y

Whereas in E, that "to retire" makes it perfectly parallel to "(to) face".

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Partially because of that potential confusion, it's not all that likely that you'll see two consecutive verbs like that in a row in a correct answer. If one answer choice says something like:

They have chosen swimming...

there's probably a better answer choice like:

They have chosen to swim...

That infinitive form is cleaner and less potentially-confusing, so if you're down between two answer choices and don't see a meaning difference or anything else, lean toward the infinitive or at least check the -ing option to see if you could potentially find some confusion there...

Hi Brian, thanks.I understand 2nd part of explanation that it is better to use infinitives but I cannot understand the rest. (may be m too dumb).cud u pls explain again.

Good Explanation Brian.
Like gmatjeet, I too went for C.