What links the two strands in a dna helix together in the middle? a. phosphate groups b. sugar rings bonded together c. proteins d. bases with hydrogen bonds

Liquid water turns into water vapor at which step in the water cycle? a. precipitation o b. water run off c. evaporation d. condensation

Which of the following is the best definition for the process of photosynthesis? a.) plants digest sugars to make energy. b.) plants use oxygen and glucose to make carbon dioxide. c.) plants use sunlight and carbon dioxide to make sugars. d.) plants use sunlight to make chlorophyll and chloroplasts.

When a gasoline engine burns gasoline, what type of chemical reaction is occurring?