He went to school _____ he was six years old. [ ]
A. until
B. yet
C. because
D. when
答案:D
季札观乐记录的是季札出使哪个国家?()
A.魏国
B.宋国
C.鲁国
D.秦国
造成高压贮液器液位过低的原因是()。
A.系统大泄漏
B.长期泄漏
C.循环损失
D.节流损失
E.膨胀损失
F.冷凝损失