Explain the ecological role of algae

They play a vital role in aquatic ecosystems by forming the energy base of the food web for all aquatic organisms. As autotrophic organisms, algae convert water and carbon dioxide to sugar through the process of photosynthesis.

the answer is c. estudió

explanation:

to translate: last year a group from my school went to cuba and studied the history of the island. you would use preterite form because it was one time and they use fue in the sentence.