Of the four nitrogen bases in DNA, which two are purines and which two are pyrimidines? Group of answer choices

uracil—thymine; guanine—cytosine

adenine—thymine; uracil—cytosine

adenine—thymine; guanine—cytosine

adenine—guanine; thymine—cytosine

The fish shown above is a tarpon. it is a fast-swimming and powerful open-water fish. its closest relatives, oddly, are burrow-dwelling conger eels that stay on the bottom. both eels and tarpon developed from snake-like larvae that float in the plankton during the first stages of life. once they mature, tarpon and eels are not found near one another in the ocean. the tarpon and the eel illustrate all of the following except

Why do leaves change color in the fall? green pigments break down and no longer mask the color of chlorophyll. chlorophyll breaks down and no longer masks the colors of other pigments. red- and yellow-colored pigments grow and mask green-colored chlorophyll. green-colored chlorophyll breaks down and turns red and yellow.

What’s the student’s scientific question