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". 

Example Input: [header] How to calculate a light year [title] Define the light year. [step] A light year is a measure of distance equal to how far light travels in one earth year. Because distances across the universe are so large, astronomers use light years. <sep> (A) However, they can also be determined by dividing by a distance. [substeps] Some light years are used year-round. (B) For light year 2014, the main determiner is the sun. In the light year, the world is filled with light bulbs. (C) Without light years, discussing the distance between two stars would require the use of large, unruly numbers. [substeps] Another measure of distance you may come across when learning astronomy is the parsec. (D) [substeps] There are two kinds of light years: day and night. The two types of light years are known as night and day.
Example Output: C

Example Input: [header] How to bend rebar [title] Understand the structural issues possible with manually-bent rebar and know how to avoid them. [step] When you bend metal, you naturally weaken it. When done correctly, however, you can minimize damage and still get the shape you need to complete the project. <sep> (A) [substeps] Badly bent rebar acts as a buffer for the metal particles of the laser beam. The piece of rebar you are bending dissolves when squeezed into contact. (B) This effect is part of the re-bend method. The process is a little different than rebending a rubber band, but the difference is that you bend it in half by simply opening up a v on each end. (C) Because of this, it's important for you to know how to modify the shape you want the rebar to be. If you have a badly bent rebar, you'll likely create grooves in the rebar that introduce excess material. (D) Keep the following in mind as you work : [substeps] Always note the grade and size of the bar you're bending, checking against the equipment you're using to ensure it works. Check with your project engineer to ensure your bends meet the minimal internal bend diameter.
Example Output: D

Example Input: A woman cleans a cafeteria floor with a mop while occasionally talking to the camera. the woman <sep> (A) uses a mop on the floor under her chair and in a bucket. (B) uses the mop around the tables and some seating areas as well as around fork corners. (C) uses a mop nozzle to clean the floor. (D) walks to and cleans a different part of the cafeteria floor.
Example Output:
D