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．The man walked sixteen miles along a dangerous road.
B．The boy walked five hours in his sleep.
C．The student habitually walked to the Iowa River and swam in his sleep.
D．The man danced a minuet in his sleep.