是指在经济发展过程中，或在工业化的不同阶段上出现的一些影响全局的、在国民经济中居于主导地位的、能带动整个经济增长的产业部门。

A．主导产业

B．先导产业

C．瓶颈产业

D．重点产业

You are a salesman in a pharmacy company. Write a letter to Mr. Wang, one of your customers, to introduce a new medicine to him.

Do not sign your own name at the end of the letter. Use "Li Ming" instead.

Do not write the address.