Xiaoshizi photography

As can be seen from the figure, the length of AB is 2cm, that is, 0.02m, and the exposure time is 1 1000s, so the average speed of AB segment is:

. v=xt=0.020.00 1=20m/s，

Because time is extremely short, the instantaneous speed of the moment corresponding to point A is about 20m/s,

According to the relationship between the velocity and displacement of free falling body v2=2gh:

h=v22g=2022× 10=20m。

So, C is correct.

So choose: C.