Answer:
A stressful situation can have negative effects on a person's body and should be avoided.
Step-by-step explanation:
The above statement best explains the idea in the underlined sentence.
Looking the underlined sentence, which is the sentence we are focusing on, it is revealed that a stressful situation can be viewed by the brain as a threat. A threat can be seen as a something dangerous. Then we are told that such stressful situation can make the body to respond in a specific way. This can lead to the contraction of the arteries. This contraction can lead to the reduction in the flow of blood.
This means that such situation has negative effects on a person's body. Such should actually be avoided.