【单选题】He’s too young ______ how to play the piano.
【单选题】Tools, work-pieces and other things must be placed on the designated appliance in the______.
【单选题】He’s too young ______ how to play the piano.
【简答题】山西省大学英语四级考试有口语考试吗?四级的具体分值是怎么安排的?
【简答题】2012年全国大学英语四级口语考试报名时间?
【单选题】半径为R 的均匀带电半圆形细环,电荷线密度为 λ 。以无限远处为电势零点,则圆心处的电势