Final answer:
To conjugate the verb 'beber' for the subject 'Ellas' in the present tense, add the ending 'en'. The correct conjugation is 'beben.'
Step-by-step explanation:
To conjugate the verb beber (to drink) in the present tense for the subject Ellas (they), you would add the ending -en. Therefore, the correct conjugation is beben. This sentence would be translated as Ellas beben limonada en el verano.
Learn more about Conjugating the verb 'beber' in Spanish