Looking for answers to an old test that I took, trying to learn what I should have done.(Malloc Function Maybe?)

Old Test

I'm going over a test I took and am trying to figure out what the answer was to these questions. I was wondering if anyone could help me? As you can probably see I did not really understand how to answer them at the time but I would like to learn. I believed the answer has something to do with Malloc, but was unsure exactly how.

Thank you!