Question

As the oic during grenade training, you observe a thrown grenade that does not explode

Answer 1

The action that should be taken is to call a cease-fire and contact Range Control. 
High explosive grenades that fail to function are not to be approached except by the explosive ordnance disposal personnel. During training, if a grenade fails to explode, the throwing of live grenades in any bay within the uninterrupted fragmentation radius of the dud grenade will cease. Dud grenades will be destroyed by EOD personnel only. Unauthorized person should not approach, move, touch, or handle dud grenades.