"Sniper", "Short range".
These are enough keywords in the question which leads anyone to infer that the bullet can and will pass through one's body to hit another person. Therefore, a more logical answer would be (3) Only K & N are safe.
If however, the one who framed the question intended in such a way that a bullet will not pass through one body, then more sensible options would've been:
1) N is unsafe
2) M is unsafe
3) L is unsafe
4) K is unsafe
5) All are safe