A significant side effect of theophylline often seen in patients is

Which of the following are effects of surface tension forces in the air-filled lung?

1. It increases the elastic recoil of the lung (promoting collapse). 2. It makes the lung harder to inflate than if it were filled with fluid. 3. It decreases the lung's elasticity as volume increases. a. 1 and 2 only b. 2 and 3 only c. 1 and 3 only d. 1, 2, and 3

Keratin is a durable protein that makes the ____ waterproof and resistant to bacteria and viruses. 

A. subcutaneous layer B. stratum basale C. epidermis D. dermis