The instructions for the genetic traits of an organism are directly determined by the

A-numbers of A, T, C and G units in a sugar molecule

B-sequence of the bases in DNA molecules

C-length of a DNA molecules

D-way the bases are paired in the two strands of a DNA molecule

The answer would be:

B. Sequence of the bases in DNA molecules.

Here is more about your questions:

DNA contain the instructions of the traits of an organism. Most of the organism have the same DNA but what makes each different is the sequence of the DNA. The sequence gives the instructions for the production of amino acid that will produce, which in turn determines what traits will be passed on or manifested by that individual.

The correct answer is D. way the bases are paired in the two strands of a DNA molecule.

The genes determines the traits of an organism and the gene is the segment of DNA which makes polypeptide. DNA is made of polynucleotide and each nucleotide consists of a phosphate, a deoxyribose sugar and a nitrogenous base. The pattern of base pairs in the DNA gives instructions for the synthesis of protein. The type of proteins determines the trait of an organisms.