Read the excerpt from "Machu Picchu: A City in the Sky.” The great Incan Empire did not last. In 1530, a Spanish army invaded the Incas’ land. Incas lived in the hidden city of Machu Picchu until the 1550s. They used this city and others in the mountains as hideouts. The Incas left the cities to fight the Spanish soldiers. Then, they returned to wait for another chance to attack. But the bronze and stone spears of the Incas were no match for the guns and cannons of the Spanish. By 1572, Spain had conquered most of the Incan Empire.

What is the best summary of the excerpt?

a)The Incan people hid in their mountain cities and avoided war with Spanish invaders in the 1550s.
b)The Incan Empire and many of its mountain cities were destroyed by Spain in the 1500s.
c)The Incan Empire is always remembered for its beautiful bronze and stone weaponry.
d)The Incan people were conquered by Spanish explorers who longed to take over the Andes Mountains.