单项选择题
A．he gave up and returned home B．he began to work towards success C．he took a journey to Hollywood D．he had difficulties in playing the small part
A．They take a completely-free bus service. B．They experimented a very cheap bus service. C．Part of the street is for buses only. D．They closed the streets to cars.
A．a solar powered engine B．engine-powered twin fans C．large flapping wings D．rotating blades