These are common safety expressions used on the rifle range to advise those on the shooter's left and right that he is about to fire.

Yes, the answer is correct. On a practice rifle range (a place to practice your shooting skills by shooting at targets that have been set up some distance away), these are things that would have been yelled out as a safety precaution, before the rifles were fired, in order to make sure no one was in the line of fire. In the Marines, the instructor would yell out these things before soldiers would be allowed to fire on a practice rifle range: 1) Is there anyone down range? (Repeat three times.) The firing line is no longer clear. 2) Firers lock and load one round into your weapon. 3) Is the firing line ready?(Is there anyone in the line of fire). 4) Ready on the right? Ready on the left? 5) Firers move your selector switch to the appropriate mode(automatic or semiautomatic) and commence firing. 6) (After firing is completed) Cease Fire, Cease Fire, Cease Fire