The correct answer is A. Right angles.
Stones (stratified rocks) are so placed in stone masonry that the direction of pressure to the plane of bedding is at right angles. This is done to prevent the stones from sliding or being pushed out of place. If the stones were placed at an angle to the plane of bedding, they would be more likely to move and could cause the structure to collapse.
Option B is incorrect because 45° is not a right angle. Option C is incorrect because 60° is not a right angle. Option D is incorrect because parallel to the plane of bedding would not provide any support against the direction of pressure.