The genetic constitution of an organism refers to the set of genes it carries within its DNA. These genes determine the specific characteristics and traits of an organism. The correct term for this genetic constitution is the genotype. The genotype is responsible for the production of proteins and other molecules that influence the development and functioning of an organism.

Here is an explanation of the given options and why the correct answer is option 'A':

A) Genotype: The genotype refers to the genetic makeup or constitution of an organism, which is determined by the specific combination of alleles (alternate forms of a gene) it possesses. The genotype is unique to each individual and is a key determinant of the organism's traits and characteristics.

B) Genome: The genome is the complete set of genetic material, including all the genes and non-coding sequences, present in an organism. It encompasses the entire DNA sequence of an organism. While the genome contains the genetic information, it does not specifically refer to the genetic constitution or combination of genes that make up an organism's genotype.

C) Trait: A trait is a specific characteristic or feature of an organism that can be observed or measured. Traits are determined by the interaction between genes and the environment. While the genotype plays a crucial role in determining traits, a single genotype can give rise to different phenotypes (observable characteristics) depending on environmental factors.

D) Phenotype: The phenotype refers to the observable characteristics or traits of an organism, which are the result of the interaction between the genotype and the environment. Phenotype includes physical features, such as eye color or height, as well as physiological and behavioral traits. While the phenotype is influenced by the genotype, it can also be influenced by environmental factors.

In summary, the genetic constitution of an organism is called the genotype, which represents the specific combination of genes an organism possesses. The genotype influences the production of proteins and other molecules that determine an organism's traits and characteristics.