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 change a drill bit [title] Loosen the chuck. [step] The chuck is piece on the end of the drill that loosens and tightens to hold the bit. Grasp the chuck with one hand while you hold the handle of the drill with your other hand. <sep> (A) Loosen the chuck by sliding the drill bit along one side. If you have known it already, it will already be loose, but there is a screw on the end of the piece that holds the bit in place. (B) Use extra leverage as you slowly press down on the chuck to loosen it. [substeps] Keep your eye on the chuck while you are tightening it. (C) Twist the chuck counterclockwise to loosen it. Another option is to pull the trigger gently while holding the chuck. (D) Begin to tighten the chuck by turning it clockwise so that the chuck remains firmly in place. Use your wooden allen or long-handled allen key to turn the chuck clockwise until it is firmly within the drill's circle.
C

[header] How to make black coffee [title] Purchase freshly roasted, whole bean coffee. [step] If you can't purchase it directly from the roaster within a week or so of it being roasted, opt for a vacuum-sealed bag from a reputable national coffee-bean roaster. [title] Purchase your own coffee grinder, or grind it in the store. <sep> (A) [step] If possible, choose a burr grinder in place of a normal blade grinder. For best results, grind the coffee fresh right before brewing each day. (B) [step] Grind coffee beans in the near-black zone of a coffee grinder. You can use either a regular-size grinder or a pre-grind grinder to grind your coffee. (C) [step] Modern coffee grinders have drawbacks, as they require higher temperatures to make purified coffee. Where possible, purchase one that comes pre-boil. (D) [step] Print it onto a piece of paper, remove the lid from the coffee grinder, and grind the coffee beans in the machine's center. [title] Unplug the coffee grinder and plug it into the wall outlet.
A

[header] How to stay healthy while traveling in the tropics [title] Get ready ahead of your trip. [step] If you are traveling to another country or even a different region of your own country, careful preparation is an important part of your trip. This can help ensure that places you visit don't present any serious health hazards and may minimize your risk of contracting an illness before you leave. <sep> (A) [substeps] If possible, get a plane ticket. A short flight either late in the night or early in the morning may be more secure than a long stay on a boat and company car. (B) [substeps] The more information you gather and advance preparations you make, the the more you can minimize the risk for health problems. [title] Inform yourself about in-country conditions. (C) When you plan to travel abroad, it is important to be on time. Make sure that you pack all of the items you will need to ensure that you won't be in a rush to get home. (D) [substeps] Pack whatever meals you will need so as to reduce your risk of hurting yourself or potentially getting sick before you leave. Cover all potential contaminants while you are flying and while traveling.
B