Answer:
1) A; 2) D; 3) B
Step-by-step explanation:
1) In option B is used as a noun; In option C sign was used as an adjective; in option D sign was used as a noun
2) Option D is a fragment, meaning that it is a dependent clause.
3) It’s really which one sounds right. You wouldn’t say [carefully, recklessly, or well] driver. It would be reckless.