在下列基因组合中，表现出相同性状的是    (    )

读下图结合所学知识，回答下列问题。

内蒙古科尔沁草原由于人口压力，超载放牧，每年以2%的速度退化，生态环境急剧恶化。1992～1996年，科研人员在科尔沁草场进行了放牧试验，主要研究不同放牧强度对草场的影响，草原的合理利用与保护。

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，并在答题卡上将该项涂黑。选项中有两项为多余选项。

                                                                       Wrong Reasons for Going to College

    A college education can be priceless.____If any of these following factors had abig influence on your decision, you're probably right to second-guess yourself.

   Because all your friends are going.

    In only a few weeks' time, the whole friend group will be scattered to a half dozen different colleges in a half dozen different places. Not to go will set yourself apart.____Because someone else expects it from you.

    Perhaps you come from a family where everyone goes to college,or maybe you're the kid that everyone is proud to believe will be the first toget there.____It's become so mucha part of the air you breathe that you've never stopped to consider whether you want to go or whether you're ready to go.

    ____It's beentough to find even a summer job. You don't have an alternative plan. Everyone else is doing it (see above). You think you might as well go to school. That isthe lamest（无说服力的）of reasons tospend $ 20,000 or more in the next year.

    Because you are afraid you'll regret it if you don't go.

    Your uncle tells you that he regrets that he didn't go tocollege. Others tell you they could have gone so much further in their career if only they had a college education.  ____ So this is not a persuasive reason for you togo to college.

a. A. Because you don't want to work.

b. Friends will wonder what's wrong with you.

c. Because you don't know what else to do.

d. Everyone seems more excited than you are.

e. It seems that for years everyone has just thought that ofcourse you'll go.

f. Whatever the story is, there are always people who regretdecisions they've made.

g. But maybe in your heart you know that you are going forthe wrong reasons.

Today there are many fires than in the past. Over 100,000 wildfires burn each year in America. Russia has 20,000 to 35,000 wildfires every year. Australia has on average 60,000 each year. These fires destroy（损害）huge areas of forests and burn hundreds of homes.

Many experts believe there are several reasons for this sudden increase in fires. The first reason is climate（气候）change. Recent weather has been warmer and drier. This leads to dangerous fire conditions. When lightening strikes（发生雷电），dry grass easily catches fire. Hot winds add to the problem. The wind spreads a fire quickly. In 2010, Russia had the hottest and driest summer in a century. In just one month, 500 fires destroyed over 2,000 homes. Some people lost their lives.

Traditional fire-fighting practices are another reason for the increase in fires. In America, firefighters used to quickly put out every fire. They didn't allow the grass and trees to burn. As a result, today many forests have thicker vegetation（植被）.Thicker vegetation means more fuel（燃料）for fires. Also, without fires from time to time, forests become overcrowded and unhealthy. Some trees are dead. The dead wood then easily catches fire. So surprisingly, America has many more fires today partly because of its past fire-fighting practices.

Scientists now understand that a fire can be a natural part of a healthy forest. As a result, countries like Australia allow more fires to burn naturally. Sometimes, fire fighters even start fires to get rid of（去除）dead wood. Of course, they carefully control the fires. The fire thins out old trees. This allows sunlight to reach the ground. As a result, fires help new trees to grow. Therefore, if a fire is not a serious threat（威胁）to people, firefighters may let it burn naturally.