You will be given a definition of a task first, then some input of the task.
In this task, you are given a context and four options. Each option is a suggested ending for the context. You should read the context and pick the best ending for the context. Please answer with "A", "B", "C", and "D".

[header] How to have healthy kidneys [title] Stay hydrated. [step] Staying properly hydrated is one of the best ways to keep your kidneys healthy. Without adequate water, your kidneys can lose some of their ability to filter your blood, and may even become damaged over the course of your lifetime. <sep> (A) [substeps] Drinking water helps your kidneys flush sodium, urea, toxins, and waste out of your body. By staying properly hydrated, you can significantly reduce your risk of developing chronic kidney disease. (B) Aim to drink at least 8 fluid ounces of water every day. This will help reduce any additional fluid or waste in your system and will also allow you to more easily relieve the symptoms of kidney problems. (C) Insufficient water will contribute to poor kidney function, such as kidney failure and rheumatoid arthritis. Trying to drink water with no filter might cause further kidney damage. (D) [substeps] The best amount of water recommended by experts is 1 gallon a day (2.5 liters) each. Drink bottled water, but you don't need soda, fruit juices, or other non-carbonated beverages; opt for bottled water.
Output:
A