细菌的内毒素是（）成分。
A.G+菌的细胞壁
B.G—菌的细胞壁
C.G+菌的肽聚糖
D.G—菌的类脂
参考答案：D
He told us he _____ a concert _____ .
A．had attended ... three days before
B．attended ... three days ago
C．would attend ... since three days
D．was attending ... for three days
保险人计算保险费的依据，也是保险人承担赔偿或者给付保险金责任的最高限额称为（）。
A.保险价值
B.保险金额
C.保险责任
D.保险范围
