---How many people will come to Beijing next year?---It’s hard to say.people I think.A. M

问题补充：

---How many people will come to Beijing next year?

---It’s hard to say.people ,I think.

A. Million of

B. Millions of

C. Three millions

D. Three millions of

答案：

A. Million of

(答案→)B. Millions of

C. Three millions

D. Three millions of

解析：根据上文，难说，可知下文为概数，表示概数时million后不加s，前面不加数字，故选B,成千上万的。