冠心病患者康复治疗合适运动量的主要标志包括:( )、( )晨起感觉舒适,无持续的疲劳感和其他不适感。
参考答案:运动时稍微出汗 轻度呼吸加快
Boys, you ____ be sitting in this room. It is for your teachers only. [ ]
A. shouldn't
B. don't have to
C. won't
D. needn't
一次混合、二次混合的填充系数为多少?