Aperson is just as likely to become dehydrated in the cold as in the heat.
a. true
b. false

The question is asking whether it is true that "A person is just as likely to become dehydrated in the cold as in the heat." - and the is is false. During the heat we often sweat, which means that our skin is covered by water - and this water evaporates, meaning that less water is left inside of us, leading to dehydration. We can still get dehydrated in the cold, just not as likely

The answer to this is true

Blood transfusions were rarely done and often fatal; they were outlawed until the nineteenth century.