The fewer restrictions there are on the advertising of legal services, the more lawyers there are who advertise their services, and the lawyers who advertise a specific service usually charge less for that service than lawyers who do not advertise. Therefore if the state removes any of its current restrictions, such as the one against advertisements that do not specify fee arrangements, overall consumer legal costs will be lower than if the state retains its current restrictions.
If the statements above are true, which of the following must be true?

Premise (facts) - 

1. "The fewer restrictions on the advertising of legal services ------ the more lawyers there are who advertise their services"

which imply: Lesser restrictions will lead to more advertisements by the lawyers

2.  The lawyers who advertise a specific service charge less for that service than lawyers who do not advertise. 

                   : The one who advertise charges lesser fee for their services.

Argument-

"Therefore if the state removes any of its current restrictions, such as the one against advertisements that do not specify fee arrangements, overall consumer legal costs will be lower than if the state retains its current restrictions.    

     Argument: If the state removes restrictions on advertisements, the consumer legal costs will decrease.

Option A: It is against the argument as if some lawyers start charging more for their services, will increase the legal cost for consumers.

Option B: The statement is far-fetched, we cannot state that more consumers will use legal services if we remove restrictions.

Option C: It is the unstated inference between the facts and the main argument. Hence the correct option.

"If the restrictions [are] ..... removed, more lawyers will advertise their services."

Option D: This statement is also far-fetched. More number of lawyers will advertise but whether other lawyers will decrease their fees is an overstatement.

Option C is correct.