The correct answer is: A. Let the water be boiled and cooled before it is kept in the fridge.
The sentence “Boil the water and cool it before you keep it in the fridge” is an imperative sentence. It is a command or instruction to the listener. The listener is being told to boil the water, cool it, and then put it in the fridge.
The first option, “Let the water be boiled and cooled before it is kept in the fridge,” is the most accurate interpretation of the sentence. It follows the order of the instructions in the sentence and does not add any extra information.
The second option, “Let the water be boiled and cooled before it is kept in the fridge by you,” is not as accurate. It adds the information that the water should be boiled and cooled by the listener. This information is not necessary to understand the sentence.
The third option, “Let the water be boiled by you and cooled by you before it is kept in the fridge,” is also not as accurate. It adds the information that the water should be boiled and cooled by the listener. This information is not necessary to understand the sentence.
The fourth option, “Let the water be boiled, cooled and kept in the fridge,” is not as accurate as the first option. It does not follow the order of the instructions in the sentence. The sentence says to boil the water and then cool it, but the fourth option says to boil, cool, and then keep the water.
Therefore, the correct answer is: A. Let the water be boiled and cooled before it is kept in the fridge.