【答案解析】With encouragement from the Chinese and American governments, schools across the United States are expanding their language offerings to include Chinese, the world's most spoken tongue, not to mention one of its most difficult to learn. After 2,400 schools expressed interest, Advanced Placement Chinese classes will be offered in high schools around the country starting next year. And the number of Chinese language programs around the country, from elementary school to adult programs, has tripled in 10 years. Up to 50,000 students are studying Chinese in elementary and secondary schools in the United States, experts estimate.