What happens after Dr. Heidiegger made the guests drink the water? A
They imagine that they are changing, when in fact it's all in their
heads.
B
They begin to grow younger and resort to their old weaknesses
and personalities.
C
They begin to grow younger and are happy but remain calm and
thoughtful.
D
They begin to grow older, though they act like they are younger.

B

Explanation:

this is b. how railways dealt with people riding the trains without paying

the following key ideas correctly express the key sentence.

restate key idea: most people can learn to swim in ten short lessons.

restate key idea: the majority of water-accident victims require mouth-to-mouth breathing.

restate key idea: an empty, tightly closed gallon jug will support a tired swimmer.  

restate key idea: first aid is to prevent accidents as well as assist in rescue.

explanation: the key idea needs to have the same topic as the key sentence (drowning and safety).