在垄断条件下，消费者支付了较高价格却消费了较少的产品数量。
参考答案：对
It is _____ he often fails in exams ________ makes his parents worried about him.
A．what; that
B．that; what
C．that; that
D．/; that
藻酸盐印模材料与胶结剂的反应极为迅速，需加入缓凝剂延缓反应进行。常用的缓凝剂是（）。
A.NaCO3
B.CaSO4
C.CanAlg
D.H3PO4
E.ZnO
