Accidents caused by car doors being opened into the path of oncoming vehicles or cyclists are common in cities. But these incidents could become a thing of the past, if doors that react to potential impacts catch on. …… The current prototype looks like a normal ear door, but an extra metal bar runs through its centre and connects to the ear’s flame between the hinges. In normal mode, the bar moves freely and doesn’t affect the door’s movement. However, if sensors detect a nearby obstacle at the same time as an accelerometer (加速度讲; 加速仪) detects an attempt to open the door, the door’s swing is restricted by a linear motor attached to the bar. The design of the intelligent door is designed in such a way that the door becomes hard to open when
A. there is an obstacle nearby. B. there is something wrong with the accelerometer. C. there is something wrong with the sensors. D. there is an accelerometer in the car.