甲船和乙船相撞，结果乙船又撞沉两艘驳船，构成()。
A.一次事故
B.两次事故
C.三次事故
D.四次事故
参考答案：A
老子的核心概念是什么？（）
A、无为
B、虚无
C、道
D、悟
His sister had to wait for him for another two hours, _______ she? [ ]
A. wasn't
B. doesn't
C. hadn't
D. didn't
