This is a suggested solution to the multiple choice question in GCE O Level Pure Physics, in Year 2011 November, paper 1, question 9.
In this question an object is being pulled by a force P along a rough horizontal surface. The correct free body diagram should be as follows:
The frictional force should always be opposite direction to motion. If the force P pulls the object to the right, then the frictional force, F must be to the left. The weight, W, is a result of the gravitational pull, hence it is downwards towards the earth.