A, the water film moves around the earth at a uniform speed with the spacecraft, and the gravity of the water film is completely used to provide centripetal acceleration, so it is in a state of complete weightlessness with the spacecraft, so A is wrong;

B, the water film is spherical because there is surface tension between water molecules, so B is correct;

C, the motion of water film is uniform circular motion, not Brownian motion. So, c is wrong;

D. Molecules will never stop moving randomly. So, d is wrong.

So choose: B.