Once upon a time, people who lived alone tended to be those on either side of marriage-twenty something professionals or widowed senior citizens.
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on side of是一句短语么，我查了词典，查不到: L3 t; i6 [& n" ~! g% ~$ S: ?
多谢大家了

people (who lived alone) tended to be what?(those on either side of marriage-twenty something professionals or widowed senior citizens).6 j& Z6 v; h/ ?4 S% n2 {7 c
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合起来一起看on either side of 在这里指两者之间。希望能有帮助

谢谢牛兄了，相当清晰