Which of the following is considered your body's first line of defense against infection?

The answer is skin.

The first line of our body defence are the barriers, may be physical or chemical. These barriers include skin, tears, mucus, cilia, stomach acid and white blood cells specially neutrophils. These barriers are always ready and prepared to defend the body from infection. Skin forms a waterproof mechanical barrier. Disease-causing germs must cross the skin and other first line of defence in order to cause diseases. If first line of defence is broken, the second line of defence within your body is activated to fight against germs.