下列不属于机械密封失效的具体表现形式的是（）。
A、磨损失效
B、腐蚀失效
C、热损伤失效
D、正常泄漏
参考答案：D
______the house was started before she went to Africa and now it is still under construction.
A．Working
B．Working at
C．Working on
D．Work on
读图：
请回答：
