检查骨关节常用方法是（）
A.MRI
B.CT
C.ECT
D.X线平片
E.超声成像
参考答案：D
The weather turned out to be fine yesterday. I ________the trouble to carry my umbrella with me.
A．should have taken
B．could have taken
C．mustn't have taken
D．needn't have taken
铝壶中的水垢（主要成分为CaCO3）可用食醋（主要成分是醋酸，可用HAC表示，AC﹣为醋酸根离子）除去，试写出这个反应的化学方程式 ____ _____ ．但如果食醋过量，还会腐蚀铝壶，方程式为 ___ ______ ．
