During the past few years, photojournalists have been gaining

I'm no expert but I'll try my best to explain this by how I thought
The writer makes the claim that photojournalism is not an art and reasons this by saying it has a practical aspect, "photojournalism is a way of recording important events," leading to the writer saying that photojournalists should be aware of this "practical aspect".

The question then asks us to strengthen this.

A Artists do not consider the monetary value of their work important.
Doesn't strengthen. So what if it's important or not to artists, what matters is whether or not photojournalists are or aren't artists.

B An object is not an object of art if the photographer pays attention to its practical use.
If an object of art is only so if the photographer doesn't pay attention to its practical use, then we should believe that photojournalists, aware of the practical use of their object, are not artists. This strengthens the conclusion by explicitly saying that the practical use of photojournalist's objects makes it so it's no longer art.

C Photojournalists should bear in mind the practical utility of their photos more than they currently do.
Even if they do bear in mind that, it doesn't make it so it's more or less art from the standpoint of "is it art now or not?" C is different from B because in B, it states that an object is art only if the photographer doesn't pay attention to its practical use, which they do (or at least sometimes do).

D Some photojournalists are more concerned than others with the practical utility of the photos they take.
I was stuck on D and B at first but why D is wrong is the same as C. In D, you get only one part of the story, you don't get any more distinction between what is art or what isn't.

E Some photos are taken for art exhibits, and are not used by the media.
Ok? Sure they might be but art can be in the media too, right? Even further, a banana isn't seen as art but in the art piece, Comedian by Maurizio Cattelan, it is.