21. What can a high school student learn in WOOT? A. Skills of novel writing. B. Basic knowledge of high school. C. Skills of solving Olympiad problems. D. Learning methods from the best students. 22. Which of the following include the strategies for taking USAMO? A. 8 practice Olympiad tests. B. 24-hour online classroom. C. 16 problem solving classes. D. 6 special classroom sessions. 23. How much should a 2019 Math Olympiad Summer Program participant pay for the registration?D.$945.A.$0.B.$150.C.$795.