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简介：Proof: Existence, ∵ can determine a plane. From the knowledge of plane geometry, we know that there are straight lines passing through points and parallel lines in it; uniqueness, assuming that there are two straight lines passing through points in space, satisfying and straight lines. According to Axiom 4, there must be There is a contradiction with ∴ There is one and only one straight line and parallel point through a straight line.