themiddlethirdof是啥意思,原句如下LookatourtopographicmapandyouwillseethatthemiddlethirdofNorthAmericancontinentfromtheRockyMountainsalmosttotheMississippiRiver--isprettyflat.

Question

the middle third of 是啥意思,原句如下
Look at our topographic map and you will see that the middle third of North American continent from the Rocky Mountains almost to the Mississippi River-- is pretty flat.

Answer 1

三等分的中间部分.
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上图中,第二个“---”就是 the middle third of “---------”