Can someone answer this

D. Adenine and Thymine form hydrogen bonds, while cytosine and guanine form covalent bonds.

Explanation:

I majored in Biology

producers within ecosystems are essential as they are at the base of the food chain. plants are examples of producers. they use the process of photosynthesis to capture light energy and use it to convert simple inorganic substances (carbon dioxide and water) into organic substances (glucose).