Given the task definition and input, reply with output. 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 adhere concrete to concrete [title] Wait for a cool, overcast day to do your concrete repairs. [step] This is the best time to adhere the concrete because it takes longer for the water to dry out, and it has more time to react with the cement. [title] Buy concrete patching material. <sep> (A) [step] It is available in a pre-mixed form or by buying the separate ingredients in bulk. If you haven't adhered concrete to concrete before, it is a good idea to go with the pre-mixed version, which only requires that you add water. (B) [step] There are many things you can purchase and use, and some of them must be custom-made. [substeps] Read the fine print of your concrete patching material. (C) [step] Before you begin patching the concrete, you may want to consider purchasing something less expensive, such as some polyurethane. Plexiglass is less expensive, and it comes in a variety of different colors. (D) [step] The concrete patching material required to adhere cement will vary widely from brand to brand, so consult the label for instructions. Concrete patching materials can be hard to find, so shop around a few different suppliers to see if someone else would be good enough.
A