If two forces P and Q (P > Q) act on the same straight line but in opposite direction, their resultant, is A. P + Q B. $$\frac{{\text{P}}}{{\text{Q}}}$$ C. $$\frac{{\text{Q}}}{{\text{P}}}$$ D. P – Q

The correct answer is D. P – Q.

The resultant of two forces acting on the same straight line but in opposite directions is the difference between the two forces. In this case, the resultant force is P – Q.

Option A is incorrect because it is the sum of the two forces. Option B is incorrect because it is the ratio of the two forces. Option C is incorrect because it is the reciprocal of the ratio of the two forces.