量反应量效曲线的原始曲线图是：
A．直线B．累加量效曲线C．对称S型曲线D．频数分布曲线E．直方双曲线
参考答案：E
Fully________to looking after three children at home，she no longer has time to enjoy the various activities in the club.
A．attached
B．occupied
C．contributed
D．devoted
战国以来的土地私有制主要有三种形式：君主私有土地、地主私有土地和自耕农私有土地。这三种形式的土地私有制在中国历史上消亡的时间分别是
A．1840 1949 1956
B．1912 1949 1978
C．1912 1952 1956
D．1840 1956 1978
