A concussion is caused by ____.

A concussion is caused by ____.
 
  a. the accumulation of tau proteins in the brain
  b. chronic traumatic encephalopathy due to multiple head injuries
  c. mechanical stress resulting from an impact to the head
  d. sensory overstimulation resulting from an impact to the head
  e. damage to nerve nets caused by exposure to explosions in combat zones

Question 2

A mild traumatic brain injury can ____.
 
  a. lead to a greater focus in concentration
  b. be metabolically beneficial
  c. lead to a depression in neuron excitability
  d. cause a contraction of brain tissue
  e. cause impaired short term memory