题目

某种RNA病毒在增殖过程中，其遗传物质需要经过某种转变后整合到真核宿主的基因组中。物质Y与脱氧核苷酸结构相似，可抑制该病毒的增殖，但不抑制宿主细胞的增殖，那么Y抑制该病毒增殖的机制是A. 抑制该病毒RNA的转录过程B. 抑制该病毒蛋白质的翻译过程C. 抑制该RNA病毒的反转录过程D. 抑制该病毒RNA的自我复制过程 阅读理解 　　In some countries in which there is very little rain at any time, the farmers have to irrigate their fields．Irrigation is easy enough if there is a great river near the crops, and if there is plenty of water in it．Canals carry the river water to the fields when necessary．In some seasons there may be too much water in the river, and the water may flood all the land near it．At other times the river water may not be enough for all the farmers, and then it will be difficult to irrigate the fields． 　　To prevent these difficulties, a dam may be built across the river．This will store water for dry seasons, and in wet seasons it will prevent the flooding of the land．A great lake will, no doubt, be formed behind the dam, and this may mean that houses and fields will be covered with water．Most people will accept that and will be ready to move to other places．Then the country can have the right amount of water at all times; more crops will be grown, there will be more food for everyone, and there will be no more floods． 　　We cannot use sea water for irrigation; the salt will not allow the crops to grow．Fresh water is always needed, and it is very difficult and costly to make fresh water from sea water．This is done in a few countries, but the fresh water is for drinking．There is not enough at present for irrigation．Perhaps a scientist will one day invent a cheaper way of producing fresh water from the sea．If fresh water could be made cheaply, we could grow more food． (1) It is easy for farmers to irrigate their fields when ________． a．there is a great river near the crops b．there is a lot of water that year c．there are many canals in the fields d．there is plenty of sea water in the country [　　] A． ab B． abc C． bcd D． abcd (2) In order to keep the country having the right amount of water at all times, ________ should be built． [　　] A． canals B． dams C． factories D． plants (3) The main idea of the passage is that ________． [　　] A． irrigation is the best way to produce more food for humans B． many ways have been tried to save water C． irrigation is necessary for farmers to have a good harvest D． scientists should try their best to make sea water fresh to meet the needs of society (4) Which of the following is NOT wrong? [　　] A． Sea water can be used to irrigate the fields． B． Scientists have found ways to take fresh water out of sea water． C． It seems that water plays little role in producing crops． D． Farmers use canals to irrigate their crops．