Why is a DNA molecule called a double helix?
A. A DNA molecule always has two strands of nucleotides.
B. Each nucleotide has two main parts: a base and a phosphate.
C. The sugar and phosphate parts are the same in all DNA molecules.
D. There are two kinds of nitrogen bases in a DNA molecule.

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.

Cells must be in osmotic equilibrium with their surroundings environments because if they swell or shrink thier membranes will rupture

How many electrons can occupy any electron orbital?