问题如下：
Which of the following statements explains a characteristic of futures price limits? Price limits:
选项：
A. help the clearinghouse manage its credit exposure.
B. can typically be expanded intra- day by willing traders.
C. establish a band around the final trade of the previous day.
解释：
A is correct. Price limits are important in helping the clearinghouse manage its credit exposure. Sharply moving prices make it more difficult for the clearinghouse to collect from parties losing money. B is incorrect because typically the exchange rules allow for an expansion of price limits the next day (not intra- day) if traders are willing. C is incorrect because price limits establish a band relative to the previous day’s settlement price (not final trade). 14
请问选项b是什么意思？