2020年3月9日19时55分，我国在西昌卫星发射中心用长征三号乙运载火箭，成功发射北斗系统第几颗导航卫星？

单项选择题会影响重力加速度的是？

单项选择题The imposition of tariffs on imports results in deadweight welfare losses for the home economy. These losses consist of the: A、Protective effect plus consumption effect B、Redistribution effect plus revenue effect C、Revenue effect plus protective effect D、Consumption effect plus redistribution effect