Answer:
B. 4 units
Explanation:
Triangle ABC is a right angled triangle. A right angle triangle has three sides (The hypotenuse which is the longest side and the other two sides which are the adjacent and the opposite).
The side facing the angle of a right angled triangle is the opposite side depending on the angle in consideration.
According to the triangle, AB = hyp = 5, BC = 3 and AC = 4
Side AB is facing the right angle, side BC is opposite to the angle A while side AC is opposite to the angle B.
Based on the conclusion in the last paragraph, it can be concluded that the length of the side opposite Angle B is AC and since the measurement of AC is 4 units, then the length we are looking for is 4 units.