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mustn’t wouldn’t shouldn’t couldn’t
was to blame for were to blame for was blamed for were blamed for
did he injure injured him was he injured he was injured
have had; are had; are had; is have had; is
If any If so When possible When necessary
another other the other others
braked would brake had braked should have braked
as usual on purpose at present by accident
braked would brake had braked should have braked
am to blame are to blame am to be blamed are to be blamed
had heart trouble had cancer had diabetes was in a car accident
having witnessed were witnessing witnessed had witnessed