简述教学工作的基本环节。
参考答案：基本环节：①备课；②上课；③课外作业的布置与批改；④课外辅导；⑤学生成绩的检查与评定。
Why don’t you bring ____ to his attention that now students are bearing too heavy a learning load?
A. it B. this that D. what
皮下埋植剂取出困难时，常用以下哪些方法辅助取出：（）
A.X线
B.CT
C.B超
D.磁共振
that D. what