Which of the following cases correctly follow the principles we have learned in this unit?

A、universitystudentspendsmuchtimeafterclasslearningacademicvocabulary;;
B、Ahighschoolstudentsmadeaweekendplantomemorizewordsthatareassociatedwithsportsasmanyaspossiblewiththehelpofwordcards;;
C、Amiddleschoolteacherisintroducingnewvocabularybyaddingandswitchingwordpartsofthenewwords;;
D、Tobetterhelpstudentsunderstandthetext,aprimaryschoolteacherspentmuchtimeexplainingdifficultwordslike“wrath”inthestorysheread;