题目

阅读理解Top Rated and Best Selling Home Coffee Makers Model Name Capacity Type, Body and Weight Key features Rating and Deal Bonavita BV 1900TS 8 Cups Drip Coffee Maker Stainless Steel Body Steel Thermal Carafe(卡夫卡瓶)Plastic is BPA-free 6.1 pounds Top Rated Coffee machine Amazing Delicious Coffee Best temperature One Touch Brew(冲泡)Programmable- Auto off Powerful and precise 1500-watt heater 4.1(502 Customer Reviews) Mr. Coffee BVMC-SJX 33GT 12 Cups Drip Coffee Maker Chrome color mixed with black Glass Ca 如图所示，用细线悬挂的带正电的小球质量为m，处在水平向右的匀强电场中．在电场力作用下，小球由最低点开始运动，经过b点后还可以向右摆动，则在小球由a摆到b这一过程中，下列说法正确的是： [　　] A． 电势能减少 B． 重力势能减少 C． 动能减少 D． 合外力做功为负