Why should plastic bags be avoided for collecting and storing biological samples containing DNA? A. They leach chemicals.
B. They are difficult to store.
C. They are expensive.
D. They retain moisture.

The large increase in atmospheric carbon dioxide in the last 50 years most likely comes from a. an increase in cellular respiration b. increased decomposition by bacteria c. an increase in the burning of fossil fuels d. an increase in photosynthesis