e.g. I should(would) helphim if I could (might).
If he could (might) have helped you, he would have done it.
B.1.If they could have sent the telegram, … 2. …. They would have started in time. 3. … if the girl might stay there for a weekend. 4. They would be glad to … 5. …if the doctor could have come in time. 6. … the students would have postponed the visit. 7. If the children could walk this distance, … 8. I should not have asked you for help if … . 9. The woman would like to speak to her sick husband if … 10/ … if he might.