题目

下列关于动物细胞工程和胚胎工程的叙述，错误的是（ ）A. 采用胚胎分割技术获得同卵双胎或多胎，可以看作动物的无性繁殖B. 细胞核移植主要在同种动物、同种组织的细胞之间进行C. 胚胎移植时，供体母畜需要具备优良的遗传性能D. 试管动物技术主要包括体外受精、早期胚胎培养和胚胎移植技术 答案：【答案】B【解析】试题分析：采用胚胎分割技术可以获得同卵双胎或多胎，可以看作动物的无性繁殖，A项正确；细胞核移植主要在不同种动物之间进行，B项错误；胚胎移植时，供体母畜需选择遗传性能和生产性能优秀的个体，C项正确；试管动物技术是指通过人工操作使卵子和精子在体外条件下成熟和 完型填空 　　One afternoon John was cutting up wood when a neighbor drove up in his car． 　　“Have you heard the 　　1　　 about the mine in Placerville?” he asked．“There was a cave - in and a miner was killed．He has three children．The 　　2　　thing is, his wife is dead．He only has a married sister who might take them 　　3　　 she lives on the other side of the Sierras．And the snow is too 　　4　　to get any mail across the mountains．” 　　John went on working, but his thoughts were on the snow - covered 　　5　　 through the mountains．He remembered 　　6　　 as a boy he had climbed snow mountains on snowshoes．He examined the wood．Then and there he decided to make a pair of snowshoes out of it． 　　After he made them he began to practise on his snowshoes until he felt 　　7　　 of himself．Then he showed his neighbors how his snowshoes 　　8　　． 　　Stepping forward, one of the town elders spoke up．“If you are ready．Go ahead and carry the mail．” With neither tracks nor paths to 　　9　　 , he moved ahead on what he believed to be the proper 　　10　　 ．As he went up the mountains the wind and cold could barely slow him down． 　　When darkness 　　11　　 ．John still moved on, guided by the stars．It was late into the night when he finally decided to stop．He must save his 　　12　　 for the long journey still ahead． 　　Finding the stump of a tree, he set it on 　　13　　 ．Then he made a platform of branches on the snow．Stretching out on it with his feet to the fire and the mailbag under his head, he fell asleep． 　　After three days of traveling, he 　　14　　 smoke curling upward from the chimneys．John knew he was nearing the town．As he glided into town, people 　　15　　 out of their homes and gathered around him．They started in 　　16　　 at the blue - eyed man on strange snowshoes． 　　“I brought you mail from Placerville,” John said simply． 　　The following day the sister of the dead miner gave John a letter, “I’ll come 　　17　　 the children as soon as the pass is clear．” She told him． 　　For the next five winters, 　　18　　 paid little, snow - shoes John went on steadily carrying the mail．For many years John was talked about as the famous mail - carrying 　　19　　 of the Far West．He was also 　　20　　 for the shoes he wore．They were the first snow - shoes, ever seen in California． (1) [　　] A． fact B． expressions C． news D． reality (2) [　　] A． sorry B． harmful C． first D． happy (3) [　　] A． and B． but C． so D． unless (4) [　　] A． cold B． freezing C． deep D． fallen (5) [　　] A． village B． part C． pass D． street (6) [　　] A． how B． what C． why D． when (7) [　　] A． tired B． proud C． afraid D． sure (8) [　　] A． did B． worked C． wore D． took (9) [　　] A． travel B． pass C． follow D． look (10) [　　] A． cause B． course C． beginning D． branch (11) [　　] A． sank B． fell C． happened D． remained (12) [　　] A． strength B． time C． food D． money (13) [　　] A． place B． bed C． board D． fire (14) [　　] A． sighted B． smelled C． heard D． tasted (15) [　　] A． kept B． poured C． picked D． stayed (16) [　　] A． public B． order C． fear D． surprise (17) [　　] A． for B． at C． on D． to (18) [　　] A． if B． however C． although D． because (19) [　　] A． passenger B． guide C． hero D． teacher (20) [　　] A． recognized B． reported C． remembered D． realized