Which scenario is an example of a matched pairs design O A A teacher compares the scores of students using a computer based method of instruction with the scores of other students using a traditional method of instruction O B A teacher calculates the average of scores of students on a pair of tests and wishes to see if this average is larger than 80 O C A teacher compares the pretest and posttest scores of students O D A teacher compares the scores of students in her class on a standardized test with the national average score