Question 489034
You were close.  3 does have infinitely many solutions, but you were not asked to find them (it would take a while!).
"2 is incorrect" is the same as "b=2 make the equation invalid" which implies that "b=2 has no solution", so 2 is a legit value as requested.
In fact, everything but 3 has this property so the answer is b not = 3.