There has been a sudden increase in the occurrence of attempts by confidence tricksters to extract money from elderly people under false pretences. This has caused the police to issue warnings to senior citizens not to let strangers into their homes. So far the police have established the following facts: Mr Froode gave £75 to a dark-haired young man posing as a representative of an insurance company. Mr Grace paid £80 to a smartly dressed 30-year-old woman who claimed that she was a financial adviser. A man who tried to trick 27-year-old Ms Dodds into paying a deposit of £100 towards the cost of a new front door was the driver of a silver grey BMW. Over a two-day period a confidence trickster has contacted more than 400 households. All of the names and addresses given by the confidence tricksters have been found to be false.

Question: The confidence tricksters may have contacted people first by telephone.
Options:
A. true, B. false, C. uncertain
Answer: "C"