教学工作的中心环节是（）
A.备课
B.上课
C.课外辅导
D.学生学业成绩的检查与评定
参考答案：B
_____ from other continents for millions of year, Australia has many plants and animals not found in any other country in the world.
A．Being separated
B．Having been separated
C．Having separated
D．To be separated
以碳黑为色素成分的字迹材料有黑油墨、碳素墨水、墨汁、（）.
A、黑铅笔
B、蓝黑墨水
C、印台油
D、打印机黑色墨盒
