Instructions: 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".
Input: [header] How to control green pond water problems [title] Have only one inch of fish per ten gallons of water. [step] Your fish can affect the pond water quality. First of all the number fish should be according to the pond size because the organic waste will be more with more fish. <sep> (A) Ideally you should have one inch of fish per ten gallons water completely. You should pay attention to the space you have in the pond and new fish you choose. (B) If you'd like, you can choose just one fish per tank. In fact, if you added more, then a total pond size of seven fish equals a while. (C) Your pond water should be the most saturated you can get. You may have at least an inch of water per ten gallons. (D) [title] Avoid direct sunlight as green water is due to small algae cell. [step] When these small algae cells come in contact with sunlight produce algae by photosynthesis.
Output:
D