In one high​ school, two teachers​ (Ms. Cheadle and Mr.​ Hendrix) have the​ highest-performing Algebra students in the​ district, while the students of the other two teachers​ (Mr. Rupp and Ms.​ Grimm) score right in the middle. Which of the following is a good example of action research that professionals at the school might​ conduct?

A. The principal decides to have all students take Algebra from Ms. Cheadle and Mr. Hendrix.
B. The superintendent asks Mr. Rupp and Ms. Grimm to take an online workshop explaining the importance of standardized testing.
C. A committee is​ formed, including all of the Algebra​ teachers, to read articles about effective math instructional strategies.
D. The teachers work together to compare lessons and​ assessments, and determine what content standards that they each teach differently.

They then choose 3 key learning objectives that they will teach using the same strategies and​ materials, and meet each week to compare​ students' scores on exit​ tickets, homework​ assignments, and quizzes.