document.write( "Question 631961: If EF is perpendicular to planes P and R, which statement must be true?\r \n" );
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document.write( "1) Plane P is perpendicular to plane Q. \n" );
document.write( "2) Plane R is perpendicular to plane P. \n" );
document.write( "3) Plane P is parallell to plane Q. \n" );
document.write( "4) Plane R is parallell to plane P. \n" );
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