Third, selection bias might be a concern as an earthquake may not be a perfectinstrument for randomization.
第三，应该注意到选择的偏差，因为地震可能不是一个随机选择的完美工具。
2
Years after stumbling upon15 his first marimba and dropping out of college to make a better one, Ron is still hard at work trying to create the perfectinstrument.
Imagine a time machine that could show you how the most perfect and essential instrument that humans possess -our voice - has been used over the course of history.