题目

下列是以酵母菌为材料进行的实验，有关叙述错误的是（ ）                     A．探究酵母菌的呼吸方式，可用溴麝香草酚蓝检测产生的CO2                       B．用酵母菌发酵酿制果酒，选择酸性重铬酸钾检测产生的酒精                       C．探究酵母菌群数量变化，应设空白对照排除无关变量干扰                          D．用稀释涂布平板法培养计数，应选择30﹣300菌落数的平板        I used to believe courtesy was a thing of the past. Very seldom have I encountered a courteous human being in this modern era.Recently, I had to change my thinking, when I came face to face with just such a human being in a coffee place, with my two daughters. The place was crowded as usual and we had to climb steep(陡峭)stairs in order to find an empty table. After enjoying coffee and snacks, we went down the narrow stairs, where there was hardly any space for another person to either climb up or come down.Just as I was in the middle of the stairs, a gentleman entered the main entrance of the restaurant which was right in front of the staircase(楼梯). I was sure I would be pushed roughly by this man going up. I kept coming down as fast as I could. My daughters were already down, looking up at me worriedly, hoping I would reach them before the stranger started walking up the stairs, knowing I was a nervous sort.Nearly reaching them, I noticed the man still standing near the door. I reached my daughters and passed the stranger at the entrance door which he kept holding open. I looked back thinking he was still at the door, deciding whether to go in or find another less crowded place. I saw him going up the stairs, two at a time. I told my daughters about it and all three of us felt bad that we did not even thank the courteous gentleman who was actually holding the door open for us ladies to pass through before going up.Such well mannered people are hard to find these days, when pushing is very common in our advanced but aggressive society. We applauded for his chivalry(骑士精神).1.What is the meaning of the underlined word “courtesy” in Paragraph 1?A. A brave action B. Sacrifice spiritC. A considerate action D. Selfish behavior2.What did the author think of the man at the first sight of him?A. He was in a hurryB. He would wait for herC. He would cross her rudelyD. He was a man with good manners3.Why did the author’s daughters worry about her?A. She was easy to be nerviousB. She took up too much spaceC. She was too old to walk fastD. She focused too much on the man4.What can we learn about the man from Paragraph 4?A. He might be a waiter of the caféB. He might have an urgent business to doC. He loved a daughter of the authorD. He would hold the door open for all