What part of the eye focuses light on the retina

The pharynx is the structure in the body that serves as a pathway of both air and food. how does the body make sure that food does not get into the lungs? the salivary glands secrete enzymes that pull food out of the air pathway. the small intestine pushes the air out of the digestive system. the pancreas breaks down food in the air pathway. the epiglottis closes the air pathway so that food will not enter it.

What could happen if two base pairs on a strand of dna or switched

How do light years astronomers to determine the ages of distant objects in space ?