Air moves out of the lungs when the
(a) diaphragm relaxes and the rib cage moves inward.
(b) air pressure inside the lungs is less than the external air pressure.
(c) diaphragm contracts and the rib cage expands.
(d) air pressure inside the lungs is the same as the external air pressure.

True or false: (a) the strings of little red dots represent carbohydrates. (b) the model is called a bilayer because there are two main types of molecules present, lipids and proteins. (c) the many black lines represent amino acid tails. (d) this model shows membrane transport. (e) the blue ovals are hydrophobic. (f) the blue ovals represent phospholipid heads.