Here are the suggested answers for the blanks in the provided sentences:

11. **Follow** these guidelines and enjoy the food you eat. (D)
12. This apartment is **suitable** for us because it is rather cheap and near the city center. (B)
13. Mr. Brown goes **to** work **by** bus every day. (A / C)
14. We may know the land well, but we know very **little** about the oceans. (D)
15. Do the following things **to have** healthy teeth. (A)

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