infinitive vs -ing form

shobhitkh - There are many different ways in which these issues may come up in Sentence Correction questions, but in most cases, what is being tested is parallelism, whether you can spot the need to keep a tense consistent in some sort of overarching construct. You can write sentences using certain verbs that fit either form without running afoul of any grammar rules. For instance,

My friend started to hike up the hill before I could get my gear.
My friend started hiking up the hill before I could get my gear.

Although a grammarian might prefer one version to another, there is nothing wrong with either one. For reference, I like the following list of rules as a general guideline, although I will be honest and say that I do not approach SC questions with such rigid considerations in mind:

https://grammar.collinsdictionary.com/us/easy-learning/the-to-infinitive-and-the-ing-form

What the GMAT™ is good at is sidetracking the test-taker with a bunch of "filler" or "fluff," and in some cases, it is easy to get lost and forget whether you need an infinitive or an -ing word instead. See, for example, official question SC04899, which starts, "As criminal activity..." (I imagine you can type in those words as a search on this site and find it.) In that case, you are faced with a few variants at the end of the underlined portion: sell, selling, and to sell. If you trace just the skeleton of the sentence, you can often arrive at the correct response without too much effort. However, I feel I should add that GMAC® categorizes that particular question as Hard for a reason, so I am guessing that many test-takers have trouble getting through all that "fluff."

If you would like to discuss specific sentences you have encountered, especially those that are NOT from the OG, I would be happy to do so here in the forum in hopes that readers may get something out of our dialogue (or add to it).

Good luck with your studies.

- Andrew