A．At the beginning of class. B．In the middle of class. C．At the end of class. D．Before the midterm exam.
参考答案A解析:When does this conversation probably take place?
推断题。根据对话的最后一句Oh, it looks like Professor Brown is here. I'll talk to you some more after class．可知该对话是在上课开始前进行的。因此，正确答案是A。
A．He was taking pictures of the scenery. B．He was waiting to attend a secret meeting. C．He was doing his job. D．The weather was bad and he could not go out.