a man can not smile like a child,（ ）a child smiles with his eyes ,while a man smile with his llips alone 填so but and还是for?为什么?

a man can not smile like a child,（ ）a child smiles with his eyes ,while a man smile with his llips alone 填so but and还是for?为什么?
a man can not smile like a child,（ ）a child smiles with his eyes ,while a man smile with his l
lips alone 填so but and还是for?为什么?

a man can not smile like a child,（ ）a child smiles with his eyes ,while a man smile with his llips alone 填so but and还是for?为什么?
填 for 因为的意思

a man can not smile like a child, for a child smiles with his eyes ,while a man smile with his lips alone
大人无法像小孩那样笑, 因为小孩笑的时候,眼睛也会笑. 而大人笑的时候,就只是用嘴巴在笑.



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for因为的意思，