对应原文：0'8"-0'36"Today I want to talk about a way in which we are able to determine how old a piece of land, or some other geologic feature is - dating techniques. I’m going to talk about a particular dating technique. Why? Good dating is a key to good analysis. In other words, if you want to know how a land formation was formed, the first thing you probably want to know is how old it is. It’s fundamental.
对应原文：1'2"-1'12"And until just recently, most of us thought the sand had come from an ancient mountain range fairly close by that flattened out over time.
解析：Until just recently提示考点，大部分人之前都认为这些砂石来源于附近一座历经岁月被风沙磨平之后古老山脉，当然这个之前的大多数人的看法一定是错的。
对应原文：3'21"-3'51"So if you measure the amount of Lead in the Zircon grain, you can figure out when the grain was formed. After that, you can determine the age of Zircon from different mountain ranges. Once you do that, you can compare the age of the Zircon in the sandstone in your sample to the age of the Zircon in the mountains. If the age of the Zircon matches the age of one of your mountain ranges, then it means the sandstone actually used to be part of that particular mountain range.
解析：从对应原文中我们可以看到, so引出了第一个步骤，measure he amount of lead和B对应;随后出现的是figure out when…formed和C选项呼应;最后通过比对得出是否是那座山的一部分，和A选项呼应。
对应原文：4'20"-4'49"...until recently, in order to do it, you really had to study many individual grains. And it took a long time before you got results. It just wasn’t very efficient. And it wasn’t very accurate. But technical advances have cut down on the number of grains you have to study, so you get your results faster. So I’ll predict that Uranium-Lead Dating is going to become an increasingly popular dating method.
对应原文：4'49"-5'15"There are a few pretty exciting possibilities for Uranium-Lead Dating. Here is one that comes to mind. You know the theory that earth’s continents were once joined together and only split apart relatively recently? Well, with Uranium-Lead Dating, we could prove that more conclusively. If they show evidence of once having been joined, that could really tell us a lot about the early history of the planet’s geology.
对应原文：2'23"-2'36"Well, as everyone in this class should know, we usually look at the grain type within sandstone, meaning the actual particles in the sandstone to determine where it came from.