>>12 is the most correct here. Let x be non-zero,
x/0 is undefined, and can be thought of as +/-∞
0/x is zero
and so 0/0 cannot be both of these at once, and so is undefined. Using algebra on equations such as x*0=0 to show that 0/0=x works for any number, as so that method can show 0/0 to be any real number, which proves its undefinability.