(2016·四川绵阳市高三二诊考试)Many teachers believe that hands－on experience is the __1__(good) way to learn. A group of students in the United States are putting that belief to the test. They __2__ (success) designed and built a robot for discovering unexplored mines __3__ the bottom of the sea. Students made the robot __4__(answer) a challenge from the U．S. Department of Defense.
