题目

There is further room for improvement in Tom’s work _________ he has achieved a lot until now. A. even though           B. as though       C. now that                 D. so that 答案：A某蔬菜基地的圆弧形蔬菜大棚的剖面如图所示，已知AB＝16m，半径OA＝10m，则中间柱CD的高度为      m．