GMAT Critical Reasoning (CR) | Re: An ingredient in coffee, known as RTC, has been found to inactivate co

An ingredient in coffee, known as RTC, has been found to inactivate common cold viruses in experiments. In previous experiments, researchers found that inactivated common cold viruses can convert healthy cells into cancer cells. It can be concluded that the use of coffee can cause cancer.
Which one of the following, if true, most seriously weakens the argument?

A) Several teams of scientists performed the various experiments, andall of the teams had similar results.
B) The carcinogenic effect