In each of the following questions, there are four sentences or parts of sentences that from a paragraph. Identify the sentence(s) that is/are incorrect in terms of grammar and usage. Then, choose the most appropriate option.
A. Peer teaching is a promising solution, where students learn by teaching and supporting their peers. 
B. AI personal tutors in such labs can enormously benefit students across all disciplines and can be a huge aid for them.
C. Aside by his solemn expression, there was nothing in the way he acted with the children that might indicate anything was wrong between them.
D. Students showed a greater interest in mathematics and made significant progress in language skills in their standard classrooms.