A study that followed the health of 420,000 people who had used a mobile phone for an average of eight and a half years, in an effort to investigate the common fear of a link between their use and cancer, has published its findings. Some of the group had used a mobile since they were first introduced 20 years ago, and fears of a link have persisted throughout that period. If such a risk did exist, even a small one, then given the very widespread use of mobile phones it could cause thousands of additional tumours. Anecdotal evidence and smaller earlier studies had suggested a higher rate of brain and neck cancer among phone users. The very large number of subjects in this study and the long period over which it was conducted mean we can have great confidence in the result. The study expected 15,000 tumours to occur in the sample population for the period, and a figure higher than this would suggest a link between the use of mobile phones and the risk of cancer.

Question: If true, the fact that more than 15,000 tumours occurred in the sample would weaken the conclusion of the passage.
Options:
A. true, B. false, C. uncertain
Answer: "B"