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A. B, C and D are the four points in space, and ab is perpendicular to CD, ad is perpendicular to BC Please give me a diagram, if it's good, I can add more points.
Take point o on triangle ABC so that point O is the perpendicular center of the triangle
So OA ⊥ BC
Because BC ⊥ ad
So BC ⊥ triangle ADO
So do ⊥ BC
Similarly, do ⊥ ab
So do ⊥ triangle ABC
So do ⊥ AC
Because of Bo ⊥ AC
So AC ⊥ triangle BDO
So AC ⊥ BD
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