1. What do you think must have been the key points they must have grappled with while working on this issue?
What do you think are ( = were) the key points they must have grappled with when working on this issue?
2. She knows how to inline skate but does not know how to figure skate.
3. Just wondering when you'll be able to send me the file. (will the choice of would over will change the meaning - slightly)
Student or Learner