有人认为鸡蛋黄的黄色跟鸡所吃的绿色植物性饲料有关，为了验证这个结论，下面哪种实验方法最可靠( )
A．选择一优良品种的蛋鸡进行实验
B．通过化验比较植物性饲料和非植物性饲料的营养成分
C．选择品种等级完全相同的蛋鸡，一半喂食植物性饲料，一半喂食非植物性饲料
D．对同一批蛋鸡逐渐增加(或减少)植物性饲料的比例
参考答案：C
解析： 为了检查题干中的因果关系(植物性饲料与蛋黄为黄色)是否为真，最可靠的是进行对比实验(求异法)：改变原因后，看结果是否不同，实验结论的可靠性取决于被实验对象只在一个方面不同，即所喂的饲料不同，在其他方面都必须相同。满足这个条件的选项是C。
Some people do not like anything to be out of place, they are never late for work, they can remember people’s birthdays; and they are always 31 to their friends and family members. Mr. Brown is such a person. Mr. Brown works in a 32 , and he lives in the town alone . He only has a sister. She lives in 33 town with her husband and her son, Mike. Mr. Brown doesn’t have time to see his sister or her family, from one year to the 34 , but he never forgets 35 them different kinds of greeting cards. These days, he is busy 36 a birthday card and presents for the 20th birthday of his nephew, Mike. Last Sunday, Mr. Brown had quite a surprise. He drove home from the hotel at the usual time, and he drove his car very 37 , not too slowly or too fast. When he got home, he parked his car as usual in the right place, and then he went into the house to make supper. Suddenly, there was a 38 the door. Mr. Brown opened the door and found a policeman standing outside the door. “What’s wrong?” he asked 39 . ‘Did I drive on the wrong side of the street? Or did I make a mistake at work?’ “Hello, Uncle,” said the policeman with a big 40 on his face, “My name is Mike”.
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根据下表计算：假如某人月工资6100元，那么他当月应纳个人所得税为（ ）
个人所得税税率表（个人工资、薪金所得减去1600元以后的余额）
| 级数 | 全月应纳税所得额 | 税率（%） |
| 1 | 不超过500元部分 | 5 |
| 2 | 超过500元至2000元部分 | 10 |
| 3 | 超过2000元至5000元部分 | 15 |
A．225元
B．550元
C．450元
D．675元