我正在上课 I was class ; I was in class
如果我正在上课 If I was in class ; If I were in school
如果这时我正在上课 If I was in class
我们正在上美术课 We are art class
现在我们正在上英语课 Now we are English class
我们现在正在上英语课 We are an English class
我正在自读所有的书，并且每个星期六都去上课。
I am reading all the books myself and attending lessons every Saturday.
正在这个时候，上课铃响，爱波伦丝太太要上课了。 她丢下一句话：“我保证当你拿到真正的成绩时，一定会很高兴。”
She said, "Oh, I'm sure you'll be quite happy when you get the grades back…" and told me to sit down as the class filed in from lunch.
到学校的时候，上课铃正在响。我刚好正点赶到教室上课。
When I got to school, the final bell was ringing. I only just made it to my class.
应用推荐