国债期货属于（）。
A.利率期货
B.汇率期货
C.股票期货
D.商品期货
参考答案：A
下列物质中，属于纯净物的是
A．碘盐
B．酱油
C．水银
D．不锈钢
— Is your father still teaching?
— Yes. It's about sixteen years ______ he started teaching. [ ]
A. until
B. after
C. since
D. with
