The leader was pragmatic in his approach to the problems facing the country.

Answer: Option B

Pragmatic : dealing with things sensibly and realistically in a way that is based on practical rather than theoretical considerations.
Optimistic : hopeful and confident about the future.
Idealistic : characterized by idealism; unrealistically aiming for perfection.
Indefinite : lasting for an unknown or unstated length of time.
Vague : of uncertain, indefinite, or unclear character or meaning.

Antonym of Pragmatic is Idealistic