b. garden
A preposition is found in a sentence in which it introduces information to the reader like a location perhaps. The object of the preposition can be a noun, a pronoun or even a gerund that is usually together with the preposition in order to complete a prepositional phrase. In the statement above, the prepositional phrase is "on the garden", therefore the preposition is "on" and the object of the preposition is the "garden" to which the preposition "on" refers to.
This is definitely true! Even if the media didn't mean to enhance the presentation of information- you will emotionally connect to the media and what the say more than you would if the information meant nothing to you.
I hope this helps!