13.

Answer and Explanation

Your Answer is

Correct Answer is C

Explanation

This question examines the logical relationship before and after. The former sentence "one purpose of these positions is to allow the patient to learn how their body responds when the horse moves", the latter sentence "the trained horse-handler ensures the safety of the patient" can be seen from the meaning of the sentence, and the latter sentence uses "of course" to indicate emphasize.

A/B/D item: in other words, for example or that is is a further explanation, but the latter sentence does not explain the content of the previous sentence, so it is wrong.