[单选题]电源系统中，IDG（整体驱动发电机）脱开电门安装在：
A. 驾驶舱49VU（头顶跳开关面板）
B. 驾驶舱120VU（后跳开关面板）
C. 前登机门过道头顶2000VU（跳开关面板）
D. 驾驶舱20VU（头顶控制面板），并有红色保护盖保护

Japanese firms have achieved the highest levels of manufacturing efficiency in the world automobile industry. 46) Some observers of Japan have assumed that Japanese firms use the same manufacturing equipment and techniques as United States firms but have benefited from the unique characteristics of Japanese employees and the Japanese culture. However, if this were true, then one would expect Japanese auto plants in the United States to perform no better than factories run by United States companies. This is not the case. 47) Japanese-run automobile plants located in the United States and staffed by local workers have demonstrated higher levels of productivity when compared with factories owned by United States companies.
Other observers link high Japanese productivity to higher levels of capital investment per worker. But a historical perspective leads to a different conclusion. 48) When the two top Japanese automobile makers matched and then doubled Unit