In sentence 8, the word <em>student's </em>should be changed to <em>students'</em>. The given text tells about a woman who became a nun and was sent to be a teacher in Calcutta, India. Every teacher has multiple students, and the text doesn't specify that Agnes was concerned about a particular student's education. This leads us to the conclusion that she was concerned about all of her students. The word <em>student's </em>would suggest that she was concerned about one student, while <em>students</em>' suggests that she was concerned about more of them. This is why option A is the correct one.
