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".
Q: [header] How to transport a horse [title] Set up the trailer. [step] Make sure that your trailer is correctly fitted and secured to your towing vehicle is well suited to towing the weight. Run a total safety check, including brake lights, tire pressure and the amount of gas in your tank. <sep> (A) Make sure that a cell phone, horse's legal and medical documents and a map or directions are in the towing vehicle. Always be prepared for problems that might occur. (B) [title] Talk to your towing company, if they allow this. [step] Remind them of their policies on towing their horses. (C) Make sure that your vehicle is not too hot before you begin towing the weight. [substeps] If you have a spare deck door, then use it to set up the trailer and also to waterproof the deck door. (D) Make sure to clamp the bed rails of the trailer. [title] Place your horses trailer on its side.
A:
A