Final answer:
In the sentence provided, 'speak' is an intransitive verb as it does not require a direct object to complete its meaning.
Step-by-step explanation:
The verb in the sentence, 'When Betsy moved to Madrid, she couldn't speak Spanish at all,' is intransitive. An intransitive verb does not require a direct object to complete its meaning in the sentence. It can stand alone with just a subject, as in the given sentence where 'Betsy' is the subject, and 'speak' is the intransitive verb. The verb 'speak' does not have a direct object following it, making it clear that Betsy is not speaking something specific into existence, but rather, the capacity to speak Spanish is what is being described.