2019－2022八下英语周报答案

4B【解析】细胞骨架是由蛋白质纤维组成的,A项错误;乙酰胆碱是一种兴奋性神经递质,与突触后膜上的特异性受体(一种特异蛋白)结合后,可引发神经冲动,而突触后膜一般是下一个神经元的细胞体膜或树突膜,B项正确;剌激必须达到一定强度才能引起神经元兴奋,才能使突触后膜的电位发生改变,C项错误;突触前积释放的乙酰胆碱与突触后膜上的特异性受体结合后,Na+通道打开,Na内流,此时膜内侧阳离子浓度比膜外侧高,膜电位表现为外负内正,D项错误

第二节书面表达One possible versionDear peterI know you are interested in ancient Chinese cultureThere is a good news that an exhibition of ancient Chineseinventions will be held in our school next Monday. It willlast for five days. We can visit it at any time duringthe exhibitionThe show will display some great inventions in ancientChina. including the world-famous Four Great Inventionsthe compass, papermaking, gunpowder and printing. Theyhad significant effects on the development of society. Forexample, thanks to papermaking and printing, a great dealof ancient information has been kept in books. These greatancient inventions made tremendous contributions to theworld civilizationooking forward to your replyLi hu

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