题目

 The cultural industry is _____ to the national economy. It is expected to account for 10% of our country’s GDP by 2015     A. valuable         B. vital                C. vague                D. valid 答案：B下图是一个几何体的三视图，其中正视图和侧视图都是一个两底长分别为和，腰长为的等腰梯形，则该几何体的体积是               （   ）．        ．       ．              ．