This is a hard question. Since the medium is the method of getting information across (such as print, internet, or video) I'd say B since this sentence focuses on the medium of footage more than the others which seem more focused on content. I'm not sure though the answer is not very clear to me.
The correct answer is: Option B. The reporter is describing rescue dogs, but the footage shows cats.
A medium is defined as an intervening element through which something is carried out from one point to another.
In this case, the medium is the element through which a news report is presented (television, radio, newspaper, internet), and Option B is the only one that refers to a medium, which is a piece of footage (video).
We’re all humans, so to feel indifference to one another (those that are suffering), is like betraying our own, according to the author. B is the best answer.
