Final answer:
The horizontal plane (H.P.) in orthographic projection should be turned in a clockwise direction up to 90 degrees to represent the object on paper, enabling the plan view to appear below the front elevation view. The answer to the question is: A. the h.p is turned in a clockwise direction up to 90 degrees.
Step-by-step explanation:
To represent an object on paper by orthographic projection, the horizontal plane (H.P.) should be placed in a specific way relative to the vertical plane (V.P.).
This action results in the plan view being on the same sheet as the front elevation in the traditional layout of orthographic drawings. Placing the horizontal plane involves visualizing it rotating about a horizontal axis until it lies in the plane of the paper. During this rotation, the top view of the object is projected downward onto the H.P. and the resulting view is then rotated into the plane of the paper for the viewer to see as if looking straight down onto the H.P.
This method ensures that the H.P. is turned about a horizontal axis from its position parallel and below the V.P. to a position perpendicular to the V.P. but still below it, effectively turning it clockwise when viewed from the right side of the object.