B. When we are talking about Hypotheses (things that we imagine):
a. use present tense forms after phrases like ‘what if’, ‘in case’ and ‘suppose’ to talk about the future if we think it is likely to happen. (e.g. Those steps are dangerous. Suppose someone has an accident.)
b. use a past tense form to talk about the future after ‘suppose’ and ‘what if’ to suggest something is not likely to happen. (e.g. It might be dangerous. Suppose they got lost.)
c. use modals ‘would’, ‘could‘ for a hypothesis about the future. (e.g. We can’t all stay in a hotel. It would be very expensive.)
d. use ‘would’ in the main clause and the past in a subordinate clause to talk about the imagined future. (e.g. I would always help someone who really needed help.)
e. We use modals with have to talk about something that did not happen in the past. (e.g. I did not see Mary, or I might have spoken to her.)