Whats the difference between a cold and a flu ?

Brainliest what are fingernails made of?

Mucous membranes.. a. cover or line external surface of body. b. line internal body surfaces that are in contact with the environment. c. produce antibodies to combat infection. d. secrete sweat, which has antibacterial enzymes.

What should you not do when doing abdominal workouts? a. keep your chin off your chest b. keep your head aligned with the spine c. put pressure on your neck d. all of the above