The question is. A multiple choise " i dont think you have any real cause ....complaint. Choices ( of / for/ with /on) Clearly it"s either of or for In my model answer it should be "for"

2" revenge was the main ....the fire . Choices ( reason for . Cause of . Reason of ) It should be " reason for"

There must be a difference between cause and reason in their usages And also prepositions ???