低碳经济是低碳发展、（）、低碳技术、低碳生活等经济形态的总称
参考答案：低碳产业
My parents__________ me to go to the movies with my friends on Saturday nights. [ ]
A. allowed
B. are allowed
C. were allowed
D. allow
随着产量的增加，厂商的平均固定成本( )。
A．等于零
B．大于零
C．先递增后递减
D．递减
E．递增
