The right answer is B) gene.
A gene, in genetics, is a basic unit of heredity which in principle predetermines a specific trait of the form of a living organism, as defined in 1909 by Wilhelm Johannsen. From the physical point of view, a gene is a fragment of the determined locus of a DNA sequence.
A gene "parameter" the synthesis of a given RNA, by predefining its structure and, therefore, that of the possible protein or possible polypeptide synthesized from this RNA: this is what molecular biology studies .
These two aspects of the notion of gene are supposed to correspond, one at the physical and molecular level, the other at the level of principle and heredity.