How does a firm determine the optimal input combination using isocost lines and isoquant curves?

By selecting the input combination that maximizes the distance between the isocost line and the isoquant curve.

By finding the point where the isocost line intersects the isoquant curve.

By finding the point where the isocost line is tangent to the highest possible isoquant curve.

By choosing the input combination that lies furthest from the origin on the isocost line.