What does the phrase "taken with a barrel of salt" mean at end of the second paragraph

A．sleepwalkers are often awakened by dangers
B．the underlying cause of sleepwalking is more serious than sleepwalking itself
C．most sleepwalkers are deranged or insane
D．All of the abov

A．It is caused by emotional conflict or guilty conscience.
B．It is the acting out of a vivid dream.
C．Somnambulists are asleep during their sleepwalking.
D．It is dangerous to waken a sleepwalker.