A:to finish, helping
B:to finish, being helped
C:finishing, helping
D:finishing,being helped
①陈独秀 ②李大钊 ③鲁迅 ④胡适 ⑤***
如图所示,物体沿斜面匀速下滑的过程中,机械能在不断减小,分析可知,在此过程中该物体减少的机械能转化为 ____能.