Hacker News Reader

>there were a number of classmates whom could not grasp

Sorry, pet peeve. It's "who". "Classmates" are the ones doing "could not grasp" instead of "could not grasp" being done to them.

Any easy trick I use to help remember which to use is to replace who/whom with he/him to see which makes more sense in the context.

"He" could not grasp. => "Who" could not grasp.

I should vote for "him" => "Whom" should I vote for?