下列有关质粒的叙述，正确的是（）

题干

下列有关质粒的叙述，正确的是（）

A：质粒是广泛存在于细菌细胞中的一种颗粒状细胞器

B：质粒是细菌细胞质中能自主复制的小型环状DNA分子

C：质粒只有在侵入宿主细胞后才能在宿主细胞内复制

D：细菌质粒的复制过程一定是在宿主细胞外独立进行的

上一题下一题 0.0难度选择题更新时间:2017-02-24 05:00:57

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B

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根据对话选词填空。

had better not , needn't, had better, would rather, mustn't

JENNY: Nick, we____go to bed. It's very late.
NICK: I know, but I ____ help Trig than go to bed. He's tearing up his English exercise book and he's throwing his grammar book round the room. I don't think he's very happy.
JENNY: Well, you ____stay up too long.
NICK: Trig, stop it. You ____ throw your books at the wall. It won't help and you might break something. You ____work at your English now. What are you learning?
TRIG: Abbreviation n 1 U abbreviating, being abbreviated 2 C shortened form of a word, phrase, etc. "Sept" an abbreviation for "September"…
NICK: But Trig, that’s from the dictionary. You ____ learn the whole dictionary by heart!

题干

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