The ______ is a device that converts electrical energy into mechanical energy in order to turn the engine over for starting. A: luxuriant B: invocation C: fatalism D: starter motor

中国大学MOOC: The following graph shows the modules of a software system, and the line in the graph shows the invocation relation between the modules. If the system is implemented and integrated using the bottom-up type, module_________ is the driver of the module b.下图显示了软件系统的模块，图中的线显示了模块之间的调用关系。 如果系统是使用自底向上类型实现和集成的，模块_________是模块b的驱动程序。