桑代克的尝试一错误学习的基本规律是效果律、__________、准备律。
参考答案：练习律
Fog and Haze occurred in many areas of our country , a large area of low visibility condition in the city.
A causing B cause C to cause D caused
致人类腹泻的细菌有（）
A.霍乱弧菌
B.肠产毒性大肠杆菌
C.肠侵袭性大肠杆菌
D.肠致病性大肠杆菌
E.肠出血性大肠杆菌
