In 1938, at the government-convened National Health Conference

When tackling a long RC passage (or any RC passage, for that matter), a good first step is to determine the purpose of each individual paragraph. Don't worry about understanding every little detail, argument, or piece of evidence in the paragraph. As long as you understand why that paragraph is there, you can always go back to it if you need further detail.

So why is the first paragraph there? It tells us that, in 1938, one group (organized labor) supported universal healthcare, and we can infer that the American Medical Association (representing physicians interests) opposed universal healthcare at that time. Cool, moving on...

The second paragraph tells us that, at least from 1915 until 1935, the AALL supported national (i.e. "universal") healthcare, while the leaders of the AFL, which supposedly represented the interests of organized labor, actually opposed the universal healthcare that organized labor would come to support by 1938. Instead, the leaders of the AFL supported voluntarism (freedom from government intrusions). Again, don't worry about every little detail; just make sure you have an idea of why that paragraph is there, which is to let us know that a major labor organization (the AFL) had opposed universal healthcare from 1915 until 1935, even though, as described in paragraph one, organized labor had come to support universal healthcare.

The purpose of paragraph three is to show that the AFL leaders made some exceptions to the voluntarism they supported from 1915 through 1935 and that part of the reason AFL leaders opposed universal healthcare was out of concern for their own power.

The fourth paragraph tells us that, while some of the AFL leaders opposed universal healthcare from 1915 to 1935, many of the unionists represented by the AFL actually supported universal healthcare. Eventually, support for universal healthcare became so prevalent among unionists that, by 1935, the AFL had officially changed its position.

Now that we know the purpose of each paragraph, we can think about the purpose of the entire passage. We have a labor organization (the AFL) that started off supporting voluntarism and opposing universal healthcare and that gradually changed its position between 1915 and 1935. The main purpose of the passage seems to be to describe the evolution of the AFL's stance on universal healthcare; this purpose fits nicely with choice (B) in question #4:

As for question #3, let's start with the purpose of that paragraph, which was to show that the AFL leaders made some exceptions to the voluntarism they supported from 1915 through 1935 and that part of the reason AFL leaders opposed universal healthcare was out of concern for their own power. Because the highlighted sentence cites examples of exceptions made by the AFL leaders to the voluntarism they supported, choice (C) is the best answer:

By taking such passages one paragraph at a time, understanding the purpose of each paragraph, and then thinking about the purpose of the entire passage, you can engage with the passage and get something out of it even if you don't understand all of the details. Since those details will always be there on the screen, you can always go back to them if needed.

I hope this helps!