期货交易是一种高级的交易方式，是以现货交易为基础、在现货交易发展到一定程度和社会经济发展到一定阶段才形成和发展起来的。（）
参考答案：对
---That actor often joins in different activities in Beijing. Do you know ____?
---For 5 years.
A．how soon he will come back
B．how long he has stayed there
C．when he went there
D．when he will come here
培养勤奋感的最佳时期是______。
A．2—3岁 B．4—5岁C．6一11岁 D．12—18岁
