With.
Roland Bartetzko of quora.
(Former Germany millitary personnel)
If a grenade is thrown in a room you’re in, what are your best chances of survival?
Your best chance to survive is to leave the room, either by the door or by jumping out of a window.
If there are no windows, you are on the 5th floor, or it’s not safe outside, you should do one of the following things:
get behind some furniture.place something between you and the grenade, for example, a flak jacket or a backpack.turn yourself away from the grenade, get flat on the ground (only if there’s enough distance between you and the grenade, at least five feet), hide your head between your arms, and cover your ears.
If you think there's enough time for it, you can try to kick the grenade in a corner where it causes less damage. Instead of your foot, however, you should use your rifle butt. Someone in the room with you might even have the guts to throw the grenade out of there.
Those are split-second decisions, based on experience and very good situational awareness. If you are new to combat, I wouldn't recommend doing it.