在空间中,①若四点不共面,则这四点中任何三点都不共线;
②若两条直线没有共点,则这两条直线是异面直线;
以上两个命题中,逆命题为真命题的是( )。(把符合要求的命题序号都填上)
②
下图曲线反映某种商品需求、供给和价格的关系,不考虑其它因索,可以推断
A.价格在P1时,该商品市场状况为供不应求
B.价格在P2时,生产者将缩小生产规模
C.价格P1→P0时,该商品的替代品需求量上升
D.需求曲线不变,该商品社会劳动生产率提高,E点将向右下方移动
—Who ______ that piano?
—My sister, when she ______ time. [ ]
A. plays; has
B. is playing; has
C. plays; is having
D. is playing; has had