I also have 2 questions about clause and preposition:
in the question " this is the Association’s most popular event, so … early to assure your place" . Answer: A.will register B.must register C.registering D.register. I chose C.registering but the right answer is D.register. Can you explain to me because after “So” may be a Phrase with Gerund?
the second question is “this novel is based … part on a true story”
Answer: A.in B.on C.by D.at. I chose B.on but the right answer is A.in. I haven’t seen Phrase " base in " before. It’s so strange for me. Can you explain to me?