课程性质 course character
必修 required (or obligatory)
必修课 a required (or obligatory) course
选修 elective
选修课 an elective course
必修课程compulsory
course或者required
course
选修课程selective
course或者elective
course
公选课:common
course或者common
required
course或者common
core
缩写这个至少我不知道怎么办
必修课
a required course; an obligatory course。
选修课
an elective course; a selective course; a selected course
course requirement: compulsary/elective