This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: C.N.S, Subject name: Medicine
The causes of systemic secondary insult to injured brain include all of the following except 
Select and explain. 
A. Hypercapnia, B. Hypoxemia, C. Hypotension, D. Hypothermia
D: Hypothermia
Answer: D: Hypothermia 
Explanation: Presumably, extreme hypercapnia produces more severe cardiovascular depression than is seen in animals subjected to lesser degrees of hypercapnia; the cardiovascular depression, in turn, leads to greater cerebral ischemia and ultimate brain damage. Prolonged hypoxia induces neuronal cell death apoptosis, resulting in a hypoxic brain injury. Cases of total oxygen deprivation are termed "anoxia", which can be hypoxic in origin (reduced oxygen availability) or ischemic in origin (oxygen deprivation due to a disruption in blood flow Emerging evidence suggests that, contrary to standard teaching, isolated brain injury may be associated with hypotension. RESULTS: The cause of hypotension was hemorrhagic in 113 (49%), isolated brain injury in 30 (13%), neurogenic in 14 (6%), and other causes in 24 (10%). Fifty (22%) were indeterminate. Ref Harrison20th edition pg 2234