You will be given a definition of a task first, then some input of the task.
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 draw blood from hard to hit veins [title] Make sure your tourniquet has been applied properly. [step] Applying a tourniquet increases the amount of blood in the vein to make them stand out more. The tourniquet should not be so tight that it cuts off the circulation. <sep> (A) This makes it hard to attach just about anything, like safety pins or bandages, to external vessels. [title] Do not put anything too heavy on the blood vessels. (B) [substeps] If it is a wrist tourniquet, you might want to remove it first. Apply the tourniquet first before you slide the string off. (C) [substeps] The tourniquet should be put on the arm about four inches above the vein. A blood pressure cuff that is inflated to 40-60 mm hg also works well. (D) [substeps] Some tourniquet manufacturers may ask you to stand to avoid any contact with blood. These tourniquet guidelines vary by manufacturer.
Output:
C