下列中产生黑色素、恶臭味及不发酵碳水化合物的为（）
A.卟啉单胞菌属
B.普氏菌属
C.密螺旋体
D.梭杆菌属
E.放线菌属
参考答案：A
—Do you regret bringing up your opinion at the meeting?
—No.________, I think it is very necessary. [ ]
A. On the contrary
B. First of all
C. On the other hand
D. In a word
