问题 选择题

正常男性精子的染色体组成可以表示为

A.22 +X

B.22 +YY

C.22 +XX

D.22十XY

答案

答案:A

题目分析:人体的体细胞中有23对染色体,22对与人体性别无关叫常染色体,决定人体性别有关的一对染色体叫性染色体。男性的一对性染色体是XY,产生一种含X染色体的精子和含Y染色体的精子两种,体细胞的染色体组成是44+XY,生殖细胞中的染色体是22+X或22+Y。女性的一对性染色体是XX,只产生一种含有X染色体的卵细胞,生殖细胞的染色体是22+X。故选项A符合题意。

阅读理解

根据短文内容,从短文后的选项中选出能填入空白处的最佳选项。选项中有两项为多余选项。

“Nature does not hurry, yet everything is accomplished.” ---Lao Tzu

If you are in a city where everyone rushes, realize that you don’t have to be like everyone else. You can be different. You can walk instead of driving in rush hour traffic. You can be on your iPhone or Blackberry less, and disconnected sometimes. Your environment doesn’t control your life---you do. I’m not going to tell you how to give you a step-by-step guide to moving slower.    1   

1. Do less.

Cut back on your projects, on your task list, on how much you try to do each day. Focus not on quantity but on quality.    2    Save smaller, routine tasks for later in the day, but give yourself time to focus.

2. Have fewer meetings.

3    And they eat into your day, forcing you to squeeze the things you really need to do into small windows, and making you rush.

3.    4   

When you do the important things with focus, without rush, there will be things that get pushed back, and that don’t get done. And you need to ask yourself: how necessary are these things? What would happen if I stopped doing them?

4. Practice mindfulness.

Simply learn to live in the present, rather than things so much about future or the past. When you eat, fully appreciate your food. When you are with someone, be with them fully. When you are walking, appreciate your surroundings, no matter where you are.

Try these things out. Life is better when unrushed.

     5    

A.Start to put off or cancel the unnecessary.

B.Meetings are usually a “big waste of time”.

C.The world likely won’t end if you don’t pass one of the examinations.

D.But here are some things to consider and perhaps adopt, if they work for your life.E. Remember the quote: if nature can get everything done without rushing, so can you.

F. Pick 2—3 important things---or even just one important thing---and work on those first.

G. Give yourself more time to get ready and get there.

单项选择题