Answer: C. After James got off his horse, he removed the saddle.
Explanation: this is a subordinated clause. The subordination is giving by the subordinate conjunction "after"; thence, we hope to find 2 parts in the sentence and in past. Therefore, options A and B would not work as they are not using any past. However, in option D, we have first simple past (preterite) and then past perfect, and this is not logically right because of the use of after in the sentence. In this sense, the only correct answer is C. After James got off his horse, he removed the saddle. Simple past + simple past.
