Part 1. 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". 
Part 2. Example
[header] How to create a christmas tree forest [title] Consider the type of tree you want to plant. [step] There are a wide variety of christmas trees and include fir, pine, spruce, cypress, and cedar. These trees thrive in different climates and look different from one another. <sep> (A) It is important to research the tree before setting up your tree to try it out to make sure you can write the tree's growing season so that you can get the most supplies you need. If you're just interested in having a tree stand out, then make sure to check for the following : [substeps] Spruce trees. (B) [substeps] Trees green may be used in a mix of green and evergreen. Greens, such as pintos and olive oil, may be more delicate than these. (C) Where the trees grow together is up to you. [substeps] Spruce trees light up the night for hours in the morning and drown out the morning sunrise between afternoons. (D) Think about where your tree forest will be located and choose a tree that can thrive in that climate. [substeps] Balsam firs are a popular christmas tree species that grow in the northern united states and canada, in hardiness zones 3-5 or states like minnesota, north dakota, and montana.
Answer: D
Explanation: This is a good example. Only option D is about Christmas trees. So, it's the correct option.
Part 3. Exercise
[header] How to improve mental math skills [title] Visualize the equation in your head. [step] The first step in solving a math problem in your head is to visualize the problem mentally. Imagine the numbers and the equation in your head. <sep> (A) As you solve portions of the problem, visualize the new numbers that you're working with. Repeating numbers mentally or verbally, in a whisper, will also help you to remember more significant numbers in the equation. (B) This way, you'll feel this new image when you see your math papers later in the day. [substeps] You may be more aware of your words and body language when you're visualizing the equation. (C) When you picture the equation, you then have a much better time because you are thinking of the process in your head, rather than the equations. [substeps] For example, imagine that math can be only done in a particular time period. (D) When you think about each answer (number, or word) create a picture about what could happen, and then try to make it into a happy picture. Once you have a picture of each answer in your head, work on how to make it into a happy picture of each part of your brain.
Answer:
A