Definition: 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 sharpen lawn mower blades [title] Disconnect the spark plug and power source. [step] A lawnmower can cause serious injury if it starts while you are working on it. Always disconnect the spark plug and the power source (outlet or battery) before disassembling your mower. <sep> (A) [substeps] The spark plug can usually be disconnected by removing a prominent wire on the side or front of the lawnmower engine from its metal mounting. Once disconnected, the engine should not be able to start. (B) Reconnecting these electric or non-electric components could potentially ruin your mower. [title] Put back your mower's fuel tank. (C) [title] Make sure to check to see if a sticker is stamped on the blades, entry holes and bindings around the blades. [title] Replace parts if you cannot find a sticker on the blades. (D) Always keep a close eye on the mower at all times, especially at night. [title] Preen your lawn and keep it clean.
Output:
A