题目

After years of hearing drivers complain about scratches (划痕) on their cars, Japan’s Nissan Motor Company has officially announced the next big thing--a paint that not only resists scratches and scrapes, but actually repairs itself within a few days. The new material, developed by Nippon Paint Company, contains an elastic rubbery-like resin (弹性树脂) that is able to heal minor (较小的) marks caused by car wash equipment, parking lot encounters, road debris (石头碎片) or even on-purpose destruction. The automaker admits its results vary depending on the temperature and the dept物体在平衡力的作用下（　　）A．一定保持静止状态B．一定做匀速直线运动C．保持静止和匀速直线运动状态D．它的运动状态可能不变