question: I am called white.  My duty is to protect and destroy.  All it takes is a sneeze and i will destroy. . .  at the sign of a cut, i will come to protect.  I will fight to my death. . .  no matter how insignificant it may be.  I am very helpful yet you can't see me.  What am i?
choices.label: A B C D E
choices.text: place white blood cell role edge separate