This does not affect the argument. Regardless of the cost to purchase a pay phone or a soft-drink machine in the 1970s, the services and goods offered by these machines were priced the same.

This does not affect the argument. We don’t know if soft drinks are among the goods whose prices increased due to inflation, or if the increase was caused by something else. It is possible that (B) does not even apply to soft drinks.

This does not affect the argument. Whether government regulation did or did not become more stringent during this period does not weaken the author’s conclusion that at the time of writing, the price of pay phone calls should be allowed to increase.

This weakens the argument. It attacks the assumption that the increase in the price of soft drinks is not due to a market condition that pay phone calls do not also face. In other words, it costs more to produce a soft drink, but not to service a phone call.

This does not affect the argument. The increased sophistication of telephone equipment does not tell us about the cost to service or price to make a phone call.