please help! i will give you 15 point and high rate
modal forms choose the correct forms of the words in italics.

1.all meetings can't be/ mustn't be a waste of time ,surely!
2.you really should have completed / must have completed the planning phase before you started executing the project
3.we still might come / must come in under budget, but it looks unlikely
4.there must have been / should have been some mistake; those are not the plans.
5.he might have been / must have been there but there were so many people that i cant say for sure