什么是拱轴线？什么是合理拱轴线？
参考答案：
拱圈各横向截面（或换算截面）的形心连线为拱轴线；合理拱轴线是拱桥上拱圈截面只受轴向压力而无弯矩作用的拱轴线。
Along with the letter was his promise ____ he wouldvisit me this coming Christmas. [ ]
A. which
B. that
C. what
D. whether
无排卵型青春期功血，大量出血时用
A．己烯雌酚B．黄体酮C．妇康片D．氯酚胺E．口服避孕药
