Given the task definition and input, reply with output. 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 stop erosion on a river bank [title] Use coir netting that's 700-900 grams per square meter (gsm). [step] Coir netting is made from coconut fibers and is biodegradable. Normal or heavy duty netting should be used when there is a large amount of water flow. <sep> (A) If you observe any decline in the water there is not much you can do to prevent erosion. [substeps] For bigger rivers (e.g. (B) [substeps] Coir netting can be purchased online or from specialty landscaping and yardwork stores. Depending on the climate conditions in your area, coir netting can last from 24 to 48 months. (C) If the water flow is moderate (0 %), bring the netting to a local bank. [substeps] The netting holds water in, preventing it from coming out. (D) Find coir netting at a local hardware store or online. [title] Mix a strong capful of regular super dish dish soap into the water and you're ready to work.
B