听力原文：In countless other ways, the people of the United States are indebted to the Mexi

听力原文： In countless other ways, the people of the United States are indebted to the Mexicans who once lived in the old Southwest. There were only 75 thousand of them when Mexico ceded the region to the United States, and these were scattered from the Gulf Coast in the east to the shores of the Pacific in the west. They had lived in the borderlands since 1598, more than twenty years before the Pilgrims sailed for the New World. In the course of more than 250 years, they had left their mark on the land. Many of the western states in the United States still bear the lovely lyrical names the Mexican settlers first wrote upon their maps. So do countless rivers and mountains, and thousands of cities and towns. Through trial and error, the rugged Mexicans had learned to survive and proper in the dry, half-desert land. When English-speaking people poured into the region, the Spanish-speaking people shared their knowledge with the new settlers, making things much easier fro them. Settlers in other parts of the United States did not have this advantage.

What does the map mean？

A．He wonders what happened to Sam.

B．He went to visit Sam' s class.

C．Sam' s class is half over.

D．Sam wants to drop the class.