真正意义上的教学主体应该是（）
A、教师
B、学生
C、教材
D、教法
参考答案：B
--- Is John doing his homework now?
--- He should, but he _______ not. He likes playing computer games.
A．must
B．could
C．need
D．may
土方边坡用边坡坡度和坡系数表示，两者互为倒数，工程中常以乃：6表示坡度（）
d, but he _______ not. He likes playing computer games.