2022-2023英语周报高一外研综合46答案

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15.A【解析】PTH是激素，发挥作用后会被灭活，而钙离子是无机盐离子，不存在灭活现象，A项错误；血钙浓度下降使PTH分泌增加，而PTH分泌增加后又会使血钙浓度回升，故血钙浓度的调节过程中存在负反馈调节，B项正确；PTH分泌增加可促进骨钙释放和肾小管对钙的重吸收，故骨细胞和肾小管上皮细胞是PTH作用的靶细胞，C项正确；钙离子通过体液的传送调节PTH的分泌，属于体液调节，PTH为激素，对血钙浓度的调节也属于体液调节，D项正确。

第二节One possible version:Mom did not say anything and she kept reading.David wasn't sure if she had heard him or not.So hecalled for help again,but Mom still seemed lost in her books.Then David realized maybe it was time for him topick up the toy train.He quietly picked it up and put it in the box.To his delight,he found that it was mucheasier to do it by himself than ask for help.Instead of going upstairs,David went to the sofa where Mom was reading.He sat down beside her andasked his mother whether she would remind him to put his dirty socks in the basket tomorrow if he left them onthe floor again.Mom put down her book and promised that she would.Since then,David not only put his dirtysocks in the basket,he also cleaned up the crumbs from the table after dinner,everyday.