What term best describes the relationship between each pair? 1 and 6; 2 and 3; 2 and 4;...

What term best describes the relationship between each pair? 1 and 6; 2 and 3; 2 and 4; 4 and 5; 5 and 8; 2 and 7; 8 and 9; 7 and 10; 11 and 12; 11 and 13; 12 and 13; 11 and 2; 11 and 3; 12 and 2; 12 and 3; 7 and 14. (Choose from identical, conformers, configurational stereoisomers, constitutional isomers, different molecular formula.)