瓷全冠的耐磨性优于（）
A.纯金铸造冠
B.钴铬合金铸造冠
C.贱金属烤瓷冠
D.硬质树脂冠
E.贵金属烤瓷冠
参考答案：A, D
Do you have any difficulty _____ these flowers? I'd like to help you if you have any. [ ]
A. to plant
B. for planting
C. with planting
D. in planting
以吐温80作增溶剂的清热口服液，最宜选用的防腐剂是
A．苯甲酸钠
B．尼泊金乙酯
C．山梨酸钾
D．苯酚
E．苯甲醇
