顶置式配气机构由正时齿轮凸轮轴、挺柱、推杠、摇臂和（）等组成。
A.气门弹簧
B.气门组
C.锁紧螺母
D.调节螺钉
参考答案：B
青春期功血的治疗原则（）
A.止血
B.减少经量
C.调整周期
D.预防癌变
E.促进排卵
ORBIS doctors work very hard _______ they can help _______ more people . [ ]
A. to, even
B. so that, many
C. that, very
D. so that, much
