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: [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.
Example solution: D
Example explanation: This is a good example. Only option D is about Christmas trees. So, it's the correct option.

Problem: [header] How to build a dog agility course [title] Create some obstacles. [step] These are important for increasing your dog's agility and running skills. [title] Make weaves (a type of obstacle dogs weave through). <sep> (A) [step] You can make those from pvc pipes as well but they are more time consuming. [substeps] The best way to do this is to buy very large, tall orange cones, line them up in a line and have your dog weave through. (B) [title] Build a bridge if it is a simple obstacle course. [title] Build a new field of seeds if this is an obstacle course. (C) [step] Make them part of your training course. [title] Consider creating a class or two for your dog because you will want the academy to know you are training. (D) [step] Also remember that the energy generated by weaving and running around obstacles can send them flying. This step is necessary if you want to move your dog for mobility.

Solution: A