Arrange the Three Lines of Defense from the First to the Last

Multiple Choice

Arrange the three lines of defense from the first to the last. 1 = Adaptive immune system
2 = Physical barriers
3 = Innate immune system

A) 1, 2, 3
B) 2, 1, 3
C) 2, 3, 1
D) 3, 1, 2
E) 3, 2, 1