题目

 By no means _____ true that all English people know their own language well. A. it is                                B. is it                           C. what is                  D. is what      答案：B9．下列叙述中，正确的是（　　）A．式量相同的物质一定是同一种物质B．分子式相同的但结构不同的物质一定属于同分异构体C．含有双键的物质一定是烯烃D．通式相同的不同物质一定属于同系物