1. Over time, most of the school children (a) will know how to use the computer for research. a)will know (correct answer) b) have known (my answer) -What is the meaning of 'over time'? - It means "some time later" 2. He reached there only (b) to find that everyone had gone. a) finding b) to find c) to be finding d) to have found - Which is correct answer and why? How should I know which one to choose? - This is a structure in English showing consecutive events: 1. he reached there and 2. he found that everyone had gone 3. The victim was moaning and was obviously (a) in great pain. a) in (correct answer) b) through (my answer) When can I use through pain? - "Through pain" means that you do something overcoming your pain. "Was is pain" - here it points out to his state - he was suffering, he was feeling pain at that moment.

https://www.quora.com/Do-people-learn-more-through-pain-or-happiness well, it may not necessarily be physical pain, but difficulties you're struggling with.

Not sure that I entirely agree that Through pain" means that you do something overcoming your pain. We got the answers out of him through pain & perserverence. :) "through pain" is difficult to use in English, I think. Maybe we'd say "because of" in cercumstances where "through" might have seemed possible.