(A) The molecular formula C8H18 with only 1oH atom corresponds to2,3 tetramethyl butane.
(B) The molecular formula C6H12 with only 2oH atom corresponds to cyclohexane.
(C) The molecular formula C6H12 with only 1o and 2oH atom corresponds to 1,1 dimethyl cyclobutane.
(D) The molecular formula C8H14 with 12 secondary and 2 tertiary H atoms corresponds to bicyclo[3.3.0]octane.