crossed below，为什么不能理解成从下面穿过？

问题如下：

A trader observes that the 50-day moving average for the S&P 500 Index recently crossed below its long-term 200-day moving average. This situation is referred to as a:

选项：

A.

death cross.

B.

golden cross.

C.

Bollinger Band.

解释：

A is correct.

A widely followed moving average crossover signal is the one that takes place between the 50-day moving average and the 200-day moving average. When the short-term (50-day) moving average crosses below the long-term (200-day) moving average, it is called a death cross and is a bearish signal.