跪谢先,我要收集骨髓液,分离单核细胞提取DNA和RNA.应该怎样保存骨髓液呢?我这里骨髓液不好收集 病例很少,1.要是-

英语达人帮帮忙,谢先~
keep sth from doing 和 preuent sth/sb from doing
这两个短语具体意思分别是什么?与他们相近的短语还有没有?把他们放进例句中举一下例,

xie和xian有什么不同
这两字发音有什么不同,我一直觉得两字发音一模一样,根本没什么区别嘛
谢先线县些这几个字,我都读做一个音的.
大家能不能帮个忙,告诉我怎么发音,

英语达人帮帮忙,谢先~
英语中but这个词有“除了”的意思,好象还有两个同意英语单词叫except和什么的单词?他们3个放在句中的位置和使用时要注意什么?最好能举3个例句.谢谢^_^

帮忙翻译这段英文! 请不要用软件翻译! 谢先!
Since its birth in the late 70s, B-Boying has been announced dead several times, but it's still alive and kicking—very much so! Today a vibrant and well connected B-Boy scene exists worldwide.
One of the most important B-Boy competitions is the Red Bull BC One, where 16 of the world's best B-Boys meet to compete and to determine in a one on one knock-out-battle who is The One.
When the spotlight is switched on, two breakers battle each other. Lose and you are out without a second chance. In the end there is one winner — the Red Bull BC One Champion.
Extraordinary artistic skills, an outstanding character, and a good reputation in the community are the success formula to get selected as a dancer for the Red Bull BC One. The challenge lies in finding influential dancers from all continents ready to set new standards and showing state of the art breaking.
B-Boy battles have their roots in ONE vs. ONE competitions. During the past 15 years one-on-one battles have been pushed to the background as crew competitions became more popular at the big events. Red Bull's objective was to go back to the roots and show B-Boying in the most spectacular and powerful way.
After an auspicious start in Biel, Switzerland (2004), the battle moved to Berlin, Germany (2005) and Sao Paulo, Brazil (2006). The 2007 Red Bull BC One Battle will take place in Johannesburg, South Africa on September 22nd.
This year, for the first time, there were 9 Red Bull BC One Qualifier Battles in different countries, where B-Boys from all over the world were able to qualify for the final battle in South Africa.
Another novelty this year was that one of the 16 B-Boys competing in each qualifier battle got selected by an online jury. Starting on April 14, B-Boys were able to qualify by uploading their profiles including photos and video footage to the Red Bull BC One website and thus get the chance to be one of the 16.
The qualifiers are over. The 16 B-Boys have been selected. Now the whole scene is anticipating the final battle in South Africa.
这是关于RedBull BCONE的介绍! 里面可能会碰到些术语! 术语空出就行!