The correct option is C helps
Let’s examine the sentence with blank no. 42: “Thus the school magazine ____(42)____ in developing the student's power of writing as well as thinking.” Blank no. 42 needs an action verb for the subject, ‘school magazine.’ The action verb should describe an action that leads to ‘developing the student's power of writing as well as thinking.’ Options A, B and C does not describe such an action and so, cannot be used. Hence, Option D is the correct answer.