In this task, you're given a question, a context passage, and four options which are terms from the passage. After reading a passage, you will get a brief understanding of the terms. Your job is to determine by searching and reading further information of which term you can answer the question. Indicate your choice as 'a', 'b', 'c', or 'd'. If you think more than one option is plausible, choose the more probable option to help you answer the question.
Q: Question: What is the normal blood pressure before it is raised? Passage:The fight-or-flight response involves nervous impulses which result in hormone secretions into the bloodstream. When a horse reacts to a threat, it may initially "freeze" in preparation to take flight. The fight-or-flight reaction begins in the amygdala, which triggers a neural response in the hypothalamus. The initial reaction is followed by activation of the pituitary gland and secretion of the hormone ACTH. The adrenal gland is activated almost simultaneously and releases the neurotransmitters epinephrine (adrenaline) and norepinephrine (noradrenaline). The release of chemical messengers results in the production of the hormone cortisol, which increases blood pressure and blood sugar, and suppresses the immune system. Catecholamine hormones, such as epinephrine and norepinephrine, facilitate immediate physical reactions associated with a preparation for violent muscular action. The result is a rapid rise in blood pressure, resulting in an increased supply of oxygen and glucose for energy to the brain and skeletal muscles, the most vital organs the horse needs when fleeing from a perceived threat. However, the increased supply of oxygen and glucose to these areas is at the expense of "non-essential" flight organs, such as the skin and abdominal organs.
 Links: a. Blood pressure b. Blood pressure c. Blood pressure d. Amygdala
A: 
a