The garner lovingly added the manure to his crops believing he was making happy flowers,what is being personified.

The flowers because they can't be happy, so they are being given human qualities which is what personification is.

Remember that a preposition describes location and is normally location based. A bee can fly around a flower, through a flower, into a flower, under a flower, and above a flower. All of the words in bold are prepositions.

Now, an object of preposition is the noun or pronoun that you are performing these actions to. It normally follows after your preposition. For example, with the bees your object of preposition is the flower. Your bee can do all of those things to the flower.

In your question, you are under the covers. If your preposition is 'under,' what are you under? What are you performing this preposition to? The answer would be b. covers.