Excess of alumina in brick earth makes the brick A. Impermeable B. Brittle and weak C. To lose cohesion D. To crack and warp on drying

The correct answer is: B. Brittle and weak.

Excess of alumina in brick earth makes the brick brittle and weak because it makes the clay more difficult to work with and less able to withstand stress. Alumina is a type of mineral that is found in clay. When there is too much alumina in the clay, it makes the clay more difficult to mix and form into bricks. It also makes the bricks more likely to crack and break when they are fired.

The other options are incorrect because:

• Option A: Impermeable. Excess of alumina does not make the brick impermeable. In fact, it can make the brick more porous, which can lead to water damage.
• Option C: To lose cohesion. Excess of alumina does not make the brick lose cohesion. In fact, it can make the brick more cohesive, which can make it more difficult to break apart.
• Option D: To crack and warp on drying. Excess of alumina can make the brick more likely to crack and warp on drying, but it does not cause the brick to do so.