不合格品油井水泥的标准？
参考答案：①如果水泥浆不符合凝固时间值
②或不符合体积稳定性的要求，则油井水泥均判为不合格品。
已知当抛物线型拱桥的顶点距水面2米时，量得水面宽8米．当水面升高1米后，水面宽度是（ ）米．
____ it comes to traffic rules, I often come across such cases _____ the local drivers obviously know
them but won't follow them. [ ]
A. If; why
B. As; which
C. Once; as
D. When; where
