This is a slightly weird question, but I'll give it a go...

The argument could be broken down as follows:
- a majority of the costs for dental care was paid by insurance companies
- therefore, it is really important for a dentist to be eligible for reimbursement by his patient's insurer
- as such, it's the insurer who decides who provides dental care

So the point (or conclusion) you're trying to disprove is that the insurer is the one that pulls the strings. Anything that helps you demolish this statement is the correct answer.

A is wrong because it only addresses the price of dental care. Since the insurer is not involved in these inexpensive procedures, this statement is not connected to our conclusion. It does not help us with the weakening of the conclusion.

B is the correct answer here. This is because statement B proves that it's not the insurer who is pulling the strings, but the state licensing agencies: if insurers MUST reimburse dentists that are licensed, then they really have no choice in this.

C is a close second. If people make the choice to go to their dentists even though they're not getting reimbursed, then the insurer would not pull the strings in dental care and the argument would be weakened. However, I personally only eliminated this option because of the word "sometimes", which means that the number of people doing this, i.e. choosing their dentists even though they won't get their money back, could be either very small (insignificant on a "modern society" scale) or a lot. I'd say C is a "bad" wrong choice

D is irrelevant to the argument because it does not have any connection to the influence of the insurers.

E is actually a strengthening statement. If people that are uninsured and they usually decide not to spend their money, then their influence in the market is pretty low. This means that the insured patients are the ones who would spend the money, so the insurer has more influence.

I didn't understand what passage says....I don't know the answer....what is the source of this question?