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 troubleshoot mold on interior walls [title] Examine areas with excessive moisture. [step] Check your home for sources of excessive moisture. These include flooding, water leaks, damp basements, hvac duct systems or shower or cooking steam. <sep> (A) Flooding may also occur from unexpected dampness level changes. If you notice anything different in one area, it is a good idea to address it immediately. (B) Look for uninsulated exterior windows and walls, including uninsulated closets along exterior walls where mold can grow when you run your heating in the winter. [substeps] Check the airflow in your home. (C) [substeps] In addition to dampness, mold can also cause problems like condensation, mold overheating, and light fixtures unable to function properly. Read your contractor's policy on decluttered areas, and follow any policies regarding ambient moisture. (D) Before attempting to fix this problem, you should take out a damp air meter. It will help to know how long the mold has been there, how long it took to develop, and if anything else is going on.
Output:
B