If the calculated net present value (NPV) is negative, which of the following must be TRUE The discount rate used is:（）

A. equal to the internal rate of return (IRR).

B. greater than the internal rate of return (IRR).

C. less than the internal rate of return (IRR).

超速时会有连续重复谐音，飞机带形态飞行时，什么速度出现（）

A.在起落架收上锁未锁住或起落架舱门未关时大于最大放起落架速度+4节

B.在缝翼或/和襟翼伸出时大于最大放襟翼速度+4节

C.以上都对