Final answer:
In the sentence provided, 'movies' is the direct object that receives the action of the verb 'watch.'
Step-by-step explanation:
The direct object in the sentence "The sisters can watch several movies without getting tired." is movies. A direct object is the noun or pronoun that receives the action of the verb. In this case, 'watch' is the verb, and what is being watched? The answer is 'movies' because 'movies' is what the sisters can watch. The other options provided do not fit the definition of a direct object. 'Watch' is the verb, 'without' is a preposition, and 'tired' is an adjective describing the sisters' condition after watching movies.