Here are some of the useful sites for SAP MM interview questions and answers:-

1) http://interviewquestionsanswerspdf.com/2014/03/sap-mm-interview-questions-and-answers/

2) https://www.tutorialspoint.com/sap_mm/sap_mm_interview_questions.htm

3) http://www.guru99.com/sap-mm-interview-questions.html

4) https://blog.udemy.com/sap-mm-interview-questions-2/

5) https://www.sapnuts.com/faq/What-MRP-procedures-are-available-in-MM-CBP-Consumption.html