NO.PZ2023010401000112
问题如下：
When the spread between 10-year U.S. Treasury yields and the federal funds rate narrows and at the same time the prime rate stays unchanged, this mix of indicators most likely forecasts future economic:
选项：
A.growth.
B.decline.
C.stability.
解释：
The narrowing spread of this leading indicator foretells a drop in short-term rates and a fall in economic activity. The prime rate is a lagging indicator and typically moves after the economy turns.
中文解析：
这一领先指标息差的收窄预示着短期利率的下降和经济活动的减少。最优惠利率是一个滞后指标，通常在经济好转后才会变动。
请问怎么看出来短期利率下降的？以及为什么短期利率下降表示经济下滑？请老师针对这题从原理角度具体分析一下，不必引用讲义，谢谢
