题目

_________ everyone is here, let’s begin the discussion.   A. Then          B. Now          C. Later          D. After 答案：B如图所示，四边形ABCD为正方形，QA⊥平面ABCD，PD∥QA，QA＝AB＝PD.则棱锥Q－ABCD的体积与棱锥P－DCQ的体积的比值是（    ）A. 2:1B. 1:1C. 1:2D. 1:3