Answer: 4
==========================================================
Rule:
If A+B = 90, then tan(A) = 1/( tan(B) ) and tan(B) = 1/( tan(A) )
-------
Since C = 90, this must mean the other two angles A and B are acute and complementary. So A+B = 90 must be the case. This allows us to use that rule above.
So,
tan(B) = 1/( tan(A) )
tan(B) = 1/( 0.25 )
tan(B) = 4
-------
Here's another way to think about it.
If tan(A) = 0.25, then we could have BC = 1 and AC = 4 as the opposite and adjacent sides respectively. That leads to tan(A) = opposite/adjacent = BC/AC = 1/4 = 0.25
When computing tan(B), the BC and AC sides swap roles in terms of opposite and adjacent,
tan(B) = opposite/adjacent = AC/BC = 4/1 = 4.
For any of these cases, we don't involve the hypotenuse AB.