According to the Information Given in the in Focus Box

According to the information given in the In Focus box: What You Really Want to Know About Sleep, which of the following statements is FALSE?

A) Research has contradicted the notion that yawning is caused by too much carbon dioxide or too little oxygen in a person's blood.
B) Deaf people who use sign language sometimes "sleep sign" during sleep.
C) Contagious yawning may have evolved as an adaptive social cue, helping groups to signal and coordinate times of activity or rest.
D) Sleep paralysis is a rare phenomenon and is usually associated with sleep disorders such as narcolepsy.