The correct answer is: A. 1 : 2
Mortar is a mixture of cement, lime, sand, and water that is used to bind bricks and other masonry units together. The proportions of lime and sand in the mortar normally used in brick construction are 1 part lime to 2 parts sand. This mixture provides a strong and durable bond between the bricks, while also allowing for some flexibility so that the structure can move with the ground.
Option B, 1 : 4, would result in a mortar that is too dry and would not provide a strong bond. Option C, 1 : 6, would result in a mortar that is too wet and would be more likely to crack. Option D, 1 : 8, would result in a mortar that is too weak and would not be able to support the weight of the bricks.
It is important to note that the proportions of lime and sand in mortar can vary depending on the type of bricks being used, the climate, and other factors. It is always best to consult with a professional mason to determine the correct proportions for your specific project.