Lisa Cox feels that the price of corn is going to rise in the future and wants to lock in a price using either a futures or forward contract. She is unfamiliar with the differences between the two instruments and asks her associate, Matt Kudrow, to explain the differences. Which of Kudrow’s comments is TRUE In futures markets, the role of the clearinghouse is to:()

A. prevent arbitrage and enforce federal regulations. 

B. act as guarantor to both sides of a futures trade. 

C. reduce transaction costs by making contract prices public.

等待程序为在NDB上空右等待，向台航迹为240°，现飞机以航向040°向NDB台飞行，加入等待程序的方法是（）。

A.直接进入

B.偏置进入

C.平行进入