问题 关于是使用this还是that的问题

The phase transitions between water and ice cause the destruction of soil skeleton, and this/that destruction lead the increases in diameter of individuals.想问一下，这里是不是使用this更好？

问题 This country has seen...是什么意思

They rushed to the scene of what may be the worst humanitarian disaster this country has seen.请问这个句子如何翻译？this country has seen...是什么意思？“国家”——“看见”？

问题 现在分词是否是作后置定的判断

Now researchers suspect that dreams are part of the mind's emotional thermostat, regulating moods while the brain is off-line.请问，regulating moods 是做thermostat的后置定语的吗？ 

问题 this在这个句子中指代什么

“Aron Ralston is an man who is interested in mountain climbing. As a mountain climber,Aron used to taking risks.This is one of the exciting things about doing in dangerous sports”最后一句中的this指代mountain climbing还是taking risks？为什么？谢谢！

话题 this

话题 this being

话题 this time

话题 this much

话题 this day

话题 this way

话题 代词this

问题 ​As a board member for/of....

As a board member for the Internet Security Research Group, she always has her pulse on the industry.这里为什么用for而不是of呢？

问题 ​As a board member for/of....

As a board member for the Internet Security Research Group, she always has her pulse on the industry.这里为什么用for而不是of呢？

问题 现在进行时与完成进行时的区分

Now the researchers are exploring methods to protect Hongyacha in its natural habitat while further studies are carried out.这里填have been exploring 是不是更好呢，强调持续在探索？求老师指点。

问题 this出现在了句子中不常见的地方

There’s this little bit of every fan that thinks theirs will be the one that stands out.这里出现this该怎么理解呢？this是怎么成分呢，是代词吗？可以用在there be后面吗？这样的用法多吗...