科学家用15N的硝酸盐作为标记物浸泡蚕豆幼苗，追踪蚕豆根尖细胞

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问题选择题

科学家用¹⁵N的硝酸盐作为标记物浸泡蚕豆幼苗，追踪蚕豆根尖细胞分裂情况，得到蚕豆根尖分生区细胞连续分裂的有关数据，如下图。下列叙述正确的是

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A．高尔基体、线粒体、叶绿体在细胞分裂过程中活动旺盛

B．蚕豆根尖细胞分裂的一个细胞周期为19.3h

C．0～2h期间，DNA分子始终处于解旋状态

D．非等位基因的自由组合可发生在19.3～21.3h

答案

答案：B

听力题

用括号内所给词的适当形式填空（每空不限一词）。（15分）

小题1:If you want keep fit, you should eat _______(little) fast food than before.

小题2:They love reading. They are ________(read) of your magazine;

小题3:Kitty enjoys cooking. She likes to cook _________(taste) meals at weekends.

小题4:People like going horse ____________(ride) in Inner Mongolia.

小题5:There _________(be) a lot of traffic on the city roads, but it got better later.

小题6:Our school football team played _________(bad) yesterday and lost the final.

小题7:I think his advice is ________(use), I don’t want to take it.

小题8:At the _________(begin), Mary didn’t feel well.

小题9:The Class1, Grade8 students ___________(plan) their class trip to the park now.

小题10:During this ________(year) Reading Week, I read the most books in my class.

小题11:My story makes the little boy ________(laugh) happily.

小题12:In cooking lessons, I can learn how ________(cook).

小题13:Our school life is different from ________(they).

小题14:Laura is a true friend. She likes to keep secrets to ____________(she).

小题15:The apples in the picture look like the real __________(one).

探究题

下表是几位同学探究实验的记录，请根据表中信息填写有关内容：

（1）若1号和2号作为一组对照实验，变量是______________；变蓝的是____________。

（2）若1号和3号作为一组对照实验，那么3号试管中还应加入的物质是________________；3号试管变蓝，由此得出结论：_________________能影响酶的消化作用。

（3）4号试管本应与1号有相同的现象，但结果出现了蓝色，你能推测少量淀粉未被消化的可能原因吗？_______________________________________________。