Which of the following words refers to urging someone strongly or advising earnestly?

The word "exhort" is an appropriate choice because it specifically conveys the idea of urging someone strongly or giving earnest advice. In its usage, "exhort" implies a passionate or fervent plea for someone to take a particular action or to adopt a specific attitude. This term is often associated with a sense of urgency and earnestness, making it the best fit for the question.

While the other words may seem related, they differ in nuance. "Advocate" generally refers to publicly supporting a cause or policy, which does not solely imply urging an individual. "Encourage" suggests providing support or confidence but may lack the same level of urgency or fervor as "exhort." On the other hand, "command" conveys authority or directive power, which differs significantly from the more supportive and earnest connotation of "exhort." Hence, "exhort" stands out as the most suitable term for the given definition.