鉴别致病性非致病性肠道杆菌的重要依据是()
A.是否发酵乳糖
B.是否发酵葡萄糖
C.是否液化明胶
D.是否产生硫化氢
E.是否产生靛基质
参考答案:A
—May I use your printer?
—________. Go ahead. [ ]
A. By all means
B. I'm afraid you can't
C. Absolutely not
D. You are welcome
常用外径来表示钢材的直径。