How will the right answer fit in terms of support and conclusion?

Only the right answer will be a conclusion guaranteed by the passage.

Highlight the main conclusion in the passage, if there is one:

There is no conclusion in the passage. The right answer will be the conclusion.

News report: [BACKGROUND]. [SUPPORT]. [BACKGROUND]. However, [SUPPORT]. Moreover, [SUPPORT].

You may not be sure which parts are support and which are background until you see the answers. But “However” and “Moreover” are pretty good signals that those statements are they key support for the conclusion in the right answer.

Map the wording of the answers to the wording of the passage:

(A) …is not appropriate for television sets with relatively small screens.

There is no info about what might be “appropriate” for “small screens”, so there’s no support for this conclusion in the passage.

(B) There is a great consumer demand…

Stop. There’s not one word about any “consumer” or “demand” in the passage.

(C) …the thicker the television set, the brighter the screen.

Just because the passage says “the larger the screen is, the dimmer it is” does NOT tells us anything about “thicker” versus thinner. A sucker bet if I ever saw one.

(D) …can now be made with screens that are both bright and very large.

Yah, that’s exactly what it was all leading to. It’s talking about exactly the same TVs that the passage describes, and “can now be made” maps perfectly to the background that they’re “recently invented”.

(E) …do not have any disadvantages….

The passage doesn’t give an exhaustive list of pros and cons, so we wouldn’t know if there are any “disadvantages” out there.

(D) is the correct answer.