The update of the machines should the most advanced technology at present. A.keep a pace of B.keep pace with C.keep pace of D.keep a pace with 答案:Bkeep pace with意为“和……同步;与……并驾齐驱”。 (2012?平顶山二模)如图所示为大型超市的自动扶梯.一人站在扶梯的水平台面上随扶梯一起匀速上升,则该人受力个数为两个两个.从扶梯底端到顶端的过程中,人的机械能增加增加(填“增加”、“不变”或“减少”).