# Problem no. 19

Geometry Level pending

An irregular tetrahedron $$ABCD$$, if there are point $$K$$ in the middle of segment $$AB$$, point $$L$$ in the middle of segment $$BC$$, point $$M$$ in the middle of segment $$CD$$, and point $$N$$ in the middle of segment $$DA$$, then $$KLMN$$ must be a $$\ldots$$

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