题目

My English teacher is really ___．She is often seen working in her office far into the night． A．warm-hearted           B．easy-going            C．hard-working         D．self-confident 答案：C如下图所示为四冲程内燃机四个冲程的示意图，箭头表示活塞的运动方向。请你结合气门的位置做出判断，其正确的工作顺序是： [     ]A．甲、丁、乙、丙 B．乙、丙、丁、甲 C．丙、甲、乙、丁D．丁、甲、丙、乙