ANS:C - 8.5 t

To explain why the reaction at support B of the beam could be 8.5 tonnes, we need to consider the equilibrium of forces acting on the beam. Assuming that the beam is in static equilibrium (not accelerating), the sum of forces in the vertical direction must be zero. When you sum the forces in the vertical direction, you take into account the weight of the beam itself and any external loads acting on it. If the beam has a distributed load or point loads applied to it, these loads contribute to the total downward force acting on the beam. The reaction at support B, being an upward force, must counteract the sum of these downward forces to maintain equilibrium. If the total downward force acting on the beam is, say, 8.5 tonnes, then the reaction at support B must be equal in magnitude but opposite in direction to balance the beam. Hence, the reaction at support B would be 8.5 tonnes.