Here's why:

* Supersonic: Refers to speeds greater than the speed of sound. The speed of sound varies slightly depending on factors like temperature and altitude, but it's roughly 1235 km/h (767 mph) at sea level.

* Subsonic: Refers to speeds slower than the speed of sound.

Since 750 km/h is less than 1235 km/h, it falls within the subsonic range.