It is estimated that one in four children aged between 4 and 11 contract head lice each year. Children in urban schools are particularly prone. Girls and boys are infected by a ratio of three to one. This is related to the fact that girls play tends to involve more prolonged contact between heads. Head lice live close to the scalp and feed on blood. The itch they cause is from the bite made when they are feeding. A louse lives for about 300 days and a female will lay over 2,000 eggs in her lifetime.

Question: The length of hair and the frequency with which it is washed are irrelevant to the likelihood of contracting head lice.
Options:
A. true, B. false, C. uncertain
Answer: "C"