发酵培养基的组成和配比由于菌种不同、设备和工艺不同等有所差异，但都包括碳源、氮源、无机盐类、生长因子等几类。
参考答案：对
A．Aging population is expected to double within decades.
B．By 2020, 45% of the people in the country will be over sixty-five.
C．Old people in this country can expect to live a longer life.
D． In less than 20 years, 23 million more people will have to retire.
企业网银投资理财的主要服务功能包括（）。
A.定期存款
B.通知存款
C.基金买卖
D.基金查询
E.集中存管银证转账
