3.  The average state requirements for high school graduation are ______ "units" of course work, while students who want to continue their study and gain admission to university usually take 20 units.
【正确答案】 B
【答案解析】 美国高中毕业生平均要拿到17.5个学分，但打算继续攻读大学的学生通常需要拿到20个学分。