Speaker A: I think Jack needs to go on a diet. He's putting on so much weight.Speaker B: ______

A．Yes, he used to be overweight.

B．Yes, I don't think highly of him.

C．How much do you think he actually weighs now

D．Do you think so I think he looks OK the way he is.

_____ 是指为完成特定的教学任务，教师和学生按一定的要求组合起来进行活动的结构。