They might keep knowledge of its potential to effect social change from being widely disseminated

The title is an excerpt from a GRE question. The test-taker is asked to fill in the blank:

Those who fear the influence of television deliberately ____ its persuasive power, hoping that they might keep knowledge of its potential to effect social change from being widely disseminated.

• promote
• underplay
• excuse
• laud
• suspect

I don't quite understand the structure and meaning of the bold part of the sentence, could you explain it for me?

Solution 1:

The bold part of the question is saying that these people are worried about other people realizing that TV has the ability to change society, and they don't want that knowledge being spread.

The sentence could be reworded as a question as:

What do those who fear the influence of television do to keep knowledge of its potential to effect social change from being widely disseminated?

So, you would be looking for a word that will not cause people to notice the power of television.

So, lets look at the possible choices:

• promote - Promoting the power of television would certainly not keep the knowledge of its ability to change the world from spreading. It would have the opposite effect.
• underplay - Underplaying the power would fit quite nicely, as it is the opposite of promote.
• excuse - This wouldn't really fit, since the people we are talking about think it is a bad thing that TV has so much power.
• laud - This is a synonym or 'praise', so it is similar to 'promote', and wouldn't fit for the same reasons.
• suspect - The people are already convinced that TV is too powerful, and 'suspecting' it would not help to keep this power secret from society at large.

So, I would choose 'underplay'.

Solution 2:

This sentence is a bit tricky to read because of its clauses. Here is how I read it

Those (who fear the influence of television) deliberately ____ its persuasive power, hoping that they might keep knowledge (of its potential to effect social change) from being widely disseminated.

You can eliminate the clauses to get an easier-to-read sentence:

They deliberately ____ its power, hoping that they might keep knowledge from being widely disseminated.

This sentence doesn't say the same thing precisely, because it doesn't say who "they" are nor what knowledge they are trying to suppress, but it illustrates the parsing.