单项选择题A．Learn the important aspect of American life.B．Bring returns back to his native land.C．Improve his language ability.D．Earn enough money to support his study.

单项选择题A．It’’s a new way of applying chemical fertilizer.B．It’’s an improved method of harvesting crops.C．It’’s a creative technique for saving labor.D．It’’s a farming process limiting the use of ploughs.