金属在轧制前后体积保持不变的客观事实叫做（）定律。
参考答案：体积不变
— ______ your telephone number? —6873214. [ ]
A. How much is
B. How many are
C. What is
D. How many is
统式喷涂设备中，空气压力总是高于流体压力
