Final answer:
The correct verb form to complete the sentence is 'supe'.
Step-by-step explanation:
The correct verb form to complete the sentence is D. supe.
The sentence begins with 'Yo', which means 'I' in English. Therefore, the correct verb form should be 'supe', which is the first-person form of the verb 'saber' (to know) in the past tense.
An example sentence is: 'Yo supe que podía comprar muchas cosas por un dólar en Ecuador.'
Learn more about Spanish verb conjugation