正确答案: B

2N

题目：外胚乳的细胞内染色体数目为( )。

解析：B

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举一反三的答案和解析：

[单选题]----You are confident about the job interview, aren’t you?---- , I’m well prepared and feel I’ve got everything they need.

Sure, I am

[单选题]71--75There were smiling children all the way. Charily they knew at what time the train passed their homes and they made it their business to stand along the railway, wave to complete strangers and cheer them up as they rushed towards Penang. Often whole families stood outside their homes and waved and smiled as if those on the trains were their favorite relatives. This is the simple village people of Malaysia. I was moved.

dull

解析：71.选D。根据第二段，作者是第一次坐长途火车，带了很多杂志看，可以看出作者一开始认为坐火车是dull（乏味的）。

[单选题]下列离子方程式正确的是

铜溶于稀硝酸：3Cu + 8H+ + 2NO3- = 3Cu2+ + 2 NO ↑+ 4H2O

解析：

【解析】A项中的氨水应写成分子式，B项发生的是氧化还原反应；C项正确；氯气具有强氧化性将S2O32－氧化成SO42－，正确的离子方程式应为S2O32－＋4Cl2＋5H2O＝2SO42－＋8Cl－＋10H＋，故D错。

【考点分析】考查离子方程式的正误判断。