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". 

Ex Input:
[header] How to choose a protein supplement [title] Choose whey protein to build muscle. [step] If you're looking for muscle-building protein, whey protein is generally your best option. Whey protein can come in the form of powder or pills and is commonly used when people are trying to build muscle via things like weight training programs. <sep> (A) By doing this, you're gaining more body fat and growing more muscle at the same time. [substeps] Whey protein can be found in half of the packaged foods. (B) Whey protein is also a low-fat protein, rich in red blood cells from bacteria. Although whey protein does not impart healthy fats to the body, whey protein helps build muscle, which you can grow and burn through exercise. (C) [substeps] Look for a whey protein powder or supplement with a high biological value. This measures how well your body can absorb the protein. (D) Whey protein occurs as a food chain, hence the slogan, " protein is fat free ". [substeps] Whey protein is complex and varies from patient to patient.

Ex Output:
C


Ex Input:
The man takes a shot at the gift wrapping. The lady finishes wrapping the gift. The man folds an edge, and the lady tapes it. the man <sep> (A) opens the package and allows the lady to remove a box lid. (B) closes and rewraps the gift. (C) squeezes her hand, and she takes a picture. (D) presents the box to the camera and talks.

Ex Output:
D


Ex Input:
[header] How to be a good mathematician [title] Develop your interest in high school. [step] Maybe you have always been fascinated by numbers and how formulas explain the world in which we live. If you think mathematics might be something you want to pursue further, focus on your math courses in high school. <sep> (A) [substeps] Ask your teachers for extracurricular activities you can participate in to hone your math skills, such as quiz bowl or mathletes. Compete in mathematics competitions such as the international mathematical olympiad. (B) Planning out your computer classroom will help you to focus on it at the very least as you educate yourself. You can attend primary school pe courses, but if you have college, you can take math courses. (C) Being a teenager doesn't mean you have to get a high school diploma to be a good mathematician. It is only a small stepping stone into a good career. (D) It's not too hard to acquire the necessary interest to get you started. You can also really look in to the focus specific to math in high school.

Ex Output:

A