题目

细胞核中转录而成的RNA要与核糖体结合来翻译相关蛋白质，需穿过几层膜？（    ） A. 0层          B. 3层          C. 8层          D. 6层 答案：A 解析: 因为RNA是生物大分子，不能自由通过膜，而细胞核膜上有核孔是大分子物质出入细胞核的通道，因此RNA是通过核孔到达细胞质中的蛋白质合成场所核糖体上，作为模板来翻译合成蛋白质的，而核糖体是无膜结构的细胞器，所以需要穿过的膜为0层。假定英语课上老师要求同桌之间交换修改作文，请你修改你同桌写的以下作文。文中共有10处错误，每句中最多有两处。错误涉及一个单词的增加、删除或修改。        增加：在缺词处加一个漏词符号（^），并在此符号下面写出该加的词。        删除：把多余的词用斜线（＼）划掉。        修改：在错的词下划一横线，并在该词下面写出修改后的词。        注意：1．每处错误及其修改均仅限一词；        2．只允许修改10处，多者（从第11处起）不计分。 My parents and I went to the park on last Sunday．There were lots of visitors stood in front of the ticket window．We waited a long time and buy three tickets．In the Tiger Mountain of the park, I was too eager to see the fierce frightened animals that I quickened my steps through the crowd．Unfortunate, I got separated from my parents．I had hard time looking for him, but I had no luck．Wandering in the park, I felt alone without any companions．Worse still, I had no money, so I had to walk home, covered as much as 5 kilometers．