Why is it possible that a unitary government might be either democratic or dictatorial in form

yes because a unitary government might be a dictatorship or  democracy .

d) the constitution rights of native americans and their right to self-government on reservations

roosevelt believed that in light of the country's recent military successes, it was unnecessary to use force to achieve foreign policy goals, so long as the military could threaten force. this belief, and his strategy of “speaking softly and carrying a big stick,” shaped much of roosevelt's foreign policy.