Answer: The entirety of sentence three best explains what a lesion is, as the answer is box three.
Explanation: A lesion is best defined as damage to organs or tissues due to underlying causes. These can be cuts or even tumors. In the context of this article, it is stated that "aphasia" is a disorder caused by "lesions in areas of the brain that are responsible for language production or comprehension; these abnormal changes in tissues often occur as a result of a stroke, brain tumor, or automobile accidents." It explicitly states that "aphasia" is caused by abnormal changes in various tissues after stating that lesions cause aphasia. By the transitive property, lesions can be caused by those same premises.