Final answer:
The word 'dreams' is a verb in the given sentence.
Step-by-step explanation:
The subject of the question is English. In this sentence, 'Ernesto de la Cruz dreams of riding the tallest waterslide in the world,' the word 'dreams' is a verb, while the phrase 'the tallest waterslide in the world' is not a verb. 'Dreams' is a verb because it shows an action (what Ernesto is doing) and can also be conjugated into different forms such as 'dreamed' or 'dreaming'.
Learn more about Parts of Speech