更换滚轮时注意事项是什么？
参考答案：更换滚轮时注意事项是人员协调配合并且断电。
-We missed you at this morning's meeting,Diana.
-________,but if I hadn't had to meet a friend,l would have been there. [ ]
A. Me,too
B. I'm sorry
C. Never mind
D. Thank you
粪便呈黑色，与下列哪种情况无关（）。
A.食用猪肝
B.服用铁剂
C.食用动物血
D.服用维生素C
E.服用铋剂
