下面设备符号中属于绝缘法兰的是（）。
A.A
B.B
C.C
D.D
参考答案：D
高于海平面300米记作______，低于海平面800米记作______．
Kate went to work _______ she was ill last week. [ ]
A. though
B. if
C. but
D. because
