英语周报外研高二2018-2023第三期答案

英语周报外研高二2018-2023第三期答案已经整理完毕，供同学们学习参考，更多英语周报答案，请关注本站。

21.A细菌易发生变异主要因为细菌繁殖速度快,易发生基因突变,细菌等原核生物和无性繁殖的直核生物都不能发生基因重组,A错误;基因重组的原因是减数分裂过程中,同源染色体上非姐妹染色单体间交叉互换或非同源染色体之间的自由组合,所以在减数第一次分裂的前、后期均可能发生,B正确:基因重组不能改变基因的“质”和“量”,但可产生新的基因型,C正确1杂合紫花豌豆自交后代中出现白花豌豆,是控制同一性状的等位基因分离的结果,而基因重组是控制不同性状的基因重新组合,D正确

第一节One possible versionear Jona,Im glad to hear from you and I' d like to share wyou something about serving chopsticksServing chopsticks are mainly used to take food fromshared dishes. You can add food to your bowl with thembut never place them into your mouth or your own bowlUsing serving chopsticks can prevent diseases from sprea-ding while we are eating together. We can alsq use them toput food into others bowls, thus creating a pleasant andharmonious dining atmosphereHoping youll come to China to experience theem afirst handYoursUa

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