Torque is a cross product, and a longer spanner loosens a stubborn bolt more easily. Which feature of the cross product does the spanner exploit?

D. That its magnitude scales with the distance from the pivot

You are buying |r|. The magnitude |r||F|sin θ scales with the lever arm, so a handle twice as long delivers twice the torque from the same push. The sin θ term earns its place too: pushing along the spanner rather than across it gives zero, which is why you push perpendicular without thinking about it.