题目

       Michelle was a student at University of California, Los Angeles. She is here to tell us how she feels about the city. What were the best things about Los Angeles?        One of my favorite things about Los Angeles is the weather. I hate the cold and it never really gets that cold there. Plus, most of the time it’s usually sunny, which is good because I love going to the beach during the summer. There’s so much to do at the beach, but my favorite thing in L.A. was having a picnic on the sand with my friends. What were the worst things about being there?     �人站在自动扶梯的水平踏板上，随扶梯斜向上匀速运动，如图所示．以下说法正确的是（ ）A．人受到重力和支持力的作用B．人受到重力、支持力和摩擦力的作用C．人受到的合外力为零D．人受到的合外力方向与速度方向相同