题干

据报道,某地空气样本中检测出A、B、C 3种抗生素的耐药性基因.只有存在于某种活菌中的耐药性基因才能感染人体.为研究此地空气中是否存在这些耐药性活菌,某研究小组做了以下实验,步骤如下.

①配置培养基并灭菌;

②制作无菌平板,并收集、培养空气中的活菌;

③对步骤②得到的活菌进行分离纯化;

④设置若干实验组和对照组,进行相关操作;

⑤将各组平板置于适宜温度的恒温箱中培养一段时间,观察菌落的生长情况.

回答下列问题:

上一题 下一题 0.0难度 选择题 更新时间:2015-06-25 04:59:04

答案(点此获取答案解析)

同类题5

阅读理解

    Businesses are witnessing a difficult time, which has in turn produced influence on consumers, desire to go green. However, shoppers are still laying stress on environmental concerns.

    Two thirds of customers say that environmental considerations inform their purchases to the same degree as they did a year ago, while more than a quarter say that they are now even better aware of the environmental effect on what they buy.

    This may help to influence how shops store goods on their shelves. And the companies should still make efforts to become more environmentally friendly. Two out of three people think it is important to buy from environmentally responsible companies, with about one in seven saying that they had even decided to take their custom elsewhere if they felt a company's environmental reputation was not good enough.

    Harry Morrison, chief executive (主管) of the Carbon Trust, sympathizes: “I understand this situation where survival is very important now. But from environmental considerations, the clock is ticking—we don't have much time. In addition, cutting carbon has an immediate effect as costs drop and a medium-term benefit for the brand.”

    Larger companies have an extra motivation to look at reducing their carbon footprint, as new rules next year will require businesses to buy carbon allowances to make up for their emissions (排放). Those that have taken early action will have a head start. More than two thirds of consumers are not clear about which companies are environmentally responsible. This suggests that firms that are able to relay clearly their message to the public will be in a pole position to attract shoppers.

    The Carbon Trust believes that it can help by informing customers about the good work companies are doing. “When companies are granted (授予) the standard, they can use a logo (标识) in all their marketing which makes it clear that they are working towards cutting emissions,” Mr. Morrison said.