Write the next sentence in the following story.

How to draw a horse's blood
Prepare the horse.
Make sure that the horse is properly restrained and is in a docile temperament before proceeding to take a blood sample. For blood collection, using a halter and rope is sufficient.

Choose from: [I] Ask someone to assist you in restraining the horse by holding the part of the rope attached to the tie ring. Using gauze soaked in alcohol, wipe the jugular furrow of the horse. [II] How this step is accomplished is dependent on the function of blood and the horse's body type. The halter needs to be large enough and wide enough to fit over the horse's body. [III] A set of cornline markers will also be handy. This will expose the horse's muzzle and the core of its larynx while drawing blood. [IV] Also make sure that there is at least an inch of rope not entangled in anything that would contain blood, such as leather, wire, or split wood. Make sure that the halter is securely covered, as you do not want to bruise the horse.. The answer should be
[I]