题目

One Sunday, Mike decided to go sailing in his boat with his friend Jack. But Jack happened to be away. Jack’s brother, John, wanted to go with him, but he didn’t know anything about sailing. Mike agreed and they started to go out to sea. Soon they found themselves in a thick fog. Mike was sure they would be hit by a big ship. Luckily, he saw a large buoy(浮标) through the fog and decided to tie(系) the boat to it for safety. As he was getting onto the buoy, however, he dropped the wet rope(绳). The boat moved away in the fog carrying John. Because John didn’t know how to use 如图所示，列车工作需用大功率电动机提供动力、列车到站前停止供电，电动机线圈随车轮转动，转变为发电机发电，此过程中车速从200km/h减到90km/h，在90km/h以下进行机械刹车，下列说法正确的是（ ）A.减速发电过程中是应用通电导体在磁场中受力的原理B.机械刹车过程是机械能转化为内能C.进站前停止供电，列车仍能继续前行是由于受到惯性力的作用D.加速行驶过程是由电动机应用了电磁感应原理