时间数列可分为（)和（)数列两类。平稳数列也就是基本上不存在趋势的数列，这类数列的各个观察值基本上在某个固定的（);非平稳数列是包含趋势性、（)性或（)性的数列。

A. whose coupon rate will increase as market rates decrease and decrease as market rates increase.
B. that may, under certain circumstances, require the bondholder to make payments to the issuer.
C. whose coupon is determined by subtracting a reference rate from some stated maximum rate.
D. that has an implicit cap on the maximum coupon rate and typically includes a floor on the minimum coupon rate.