Q: 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 dispose of burnt firewood and ash safely [title] Allow the wood and ashes to cool completely in the fireplace. [step] If indoors, let your embers cool down completely with the fire screen closed. Even if it appears the ashes and wood aren't hot, they may remain warm and capable of starting a fire for some time. <sep> (A) [substeps] Leaving your embers out on a sunny rooftop, for example, will make it difficult for smoke to escape from the room. Placing several smokers on this rooftop is safer for the building than putting them on a shared porch, which would cause them to burn out. (B) [substeps] This should only be done if the ash touches a fireplace surface. [title] Provide your kindling at least 15 inches (30 cm) over wood shelf height. (C) [substeps] Leaving burned wood out in the air creates carbon dioxide, which traps organic compounds. The ashes can then be reused to add gas to your stove or any other flammable surface. (D) Allow several hours for the embers to cool. They will not radiate any heat when they are completely cold.
A:
D