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The argument that humans，even in prehistoric times，had some number sense，at least to the extent of recognizing the concepts of more and less when some objects were added to or taken away from a small group，seems fair.for studies have shown that some animals possess such a sense.

人类甚至在史前已经有数字感，至少到有些物体被加到一小组里或者被拿走时能够辨别出“多了”还是“少了”的程度，这一观点似乎很合理，因为研究已经表明有些动物就有这样的意识。

The primary reason was skepticism that a railroad built through so challenging and thinly settled a stretch of desert，mountain，and semiarid plain could pay a profit.

主要原因是存在一种怀疑主义，人们怀疑途经如此富于挑战性、人口稀疏的大片沙漠、山脉和半干旱平原的一条铁路能否获得利润。

延伸阅读：

托福听力中高频短语真题解析（二）

托福听力中高频短语真题解析（三）

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