迅速出血后出现休克症状，表明至少已丢失全身总血量的    A．10%    B．15%    C．20%    D．25%    E．30%

单项选择题教材的主体部分是( ) A. 讲授提纲和讲义 B. 教科书和参考书 C. 教科书和讲义 D. 讲义和参考书

单项选择题Inspection certificate issued by Chinese inspection authorities is valid for (x) days for general products and only for (y) days for perishable goods. Please find the right number of days in the following combinations. ( ) A、x=30 and y=30 B、x=60 and y=14 C、x=60 and y=7 D、x=20 and y=15