直流斩波器可以把直流电源的固定电压变为可调的直流电压输出。
参考答案：对
Under which of the following conditions would a firm be most likely to issue variable-rate debt（）
A. Operating cash flows are positively correlated with short-term interest rates.
B. Operating cash flows are negatively correlated with short-term interest rates.
C. The yield curve is sloping sharply downward.
下列那种隧道施工方法不属于钻爆法（）。
A.全断面开挖法
B.台阶法
C.盾构法
