Read the excerpt below from steve jobs: the man who thought different and answer the question.

before the adoption could be finalized, however, she learned that neither parent had a college degree. she balked and only agreed to complete the adoption a few months later, “when my parents promised that i would go to college,” said jobs.
what is the meaning of the word "balked" as it is used in the excerpt?

accepted
protested
squawked
encouraged