Hi Onell,

We cannot use a comma preceding a "to verb" (an infinitive). This is a rule that we should follow in GMAT and otherwise in written written as well. This rule is a generally accepted rule. This is the reason why Choice E is incorrect.

The source that you refer to in your post actually lists a very detailed framework on various possible constructions with "to verb". If you read that page in its entirety you will find the following take away messages:

If "to verb phrase" is used at the beginning of the main clause, then it must be separated by a comma. In this case, "to verb phrase" precedes the comma.

However, if "to verb phrase" appears at the end of the main clause, then it must not be separated by a comma.

Thanks,

Payal