The correct answer is: A. The same line in the same sense.
Two forces acting at a point are in equilibrium if the net force acting on the point is zero. This means that the forces must be equal in magnitude and opposite in direction. In other words, they must be along the same line in the same sense.
Option B is incorrect because the forces do not need to be along the same line. For example, two forces acting at a point on a lever can be in equilibrium if they are along different lines, but they must be equal in magnitude and opposite in direction.
Option C is incorrect because the forces do not need to be perpendicular to each other. For example, two forces acting at a point on a string can be in equilibrium if they are along the same line, but they must be equal in magnitude and opposite in direction.
Option D is incorrect because it is not one of the possible answers.