某人患甲状腺肿大症，他缺乏的元素主要是[ ]
A．铁元素
B．钙元素
C．磷元素
D．碘元素
答案：D
York, _____ last year, is a nice old city. [ ]
A. that I visited
B. which I visited
C. where I visited
D. in which I visited
烤瓷基底冠的尖锐棱角易造成（）
A.瓷层断裂
B.底冠变形
C.底冠断裂
D.瓷层变形
E.瓷层气泡
