The correct answer is option 'C': genotype.

Genetic constitution of an organism:

- The genetic constitution of an organism refers to the specific combination of genes present in its DNA.
- It determines the characteristics and traits of an organism, including its physical appearance, behavior, and physiological processes.
- The genetic constitution is unique to each individual and is inherited from its parents.

Understanding the options:

a) Trait: A trait refers to a specific characteristic or feature of an organism that can be observed or measured, such as eye color, height, or flower color. Traits are determined by the genes present in an organism's genetic constitution.

b) Genome: The genome refers to the complete set of genetic material (DNA) present in an organism. It includes all the genes, non-coding regions, and other DNA sequences. The genome contains all the information required to build and maintain an organism.

c) Genotype: Genotype refers to the genetic makeup of an organism, specifically the combination of alleles (different forms of a gene) present in its DNA. It represents the specific genetic information that an organism carries, regardless of whether it is expressed or visible.

d) Phenotype: Phenotype refers to the observable traits or characteristics of an organism. It is the result of the interaction between an organism's genotype and its environment. Phenotype includes both physical traits (such as hair color, eye color) and physiological traits (such as blood type, enzyme production).

Explanation of the correct answer:

The genetic constitution of an organism is called its genotype. This term specifically refers to the genetic makeup or combination of alleles present in an organism's DNA. The genotype determines which traits or characteristics an organism can potentially have, although not all traits may be expressed in the phenotype. The genotype serves as the blueprint for the development and functioning of an organism, and it is inherited from the organism's parents through the process of reproduction.

The phenotype, on the other hand, refers to the observable traits or characteristics of an organism that result from the interaction between its genotype and the environment. The phenotype can be influenced by various factors, including gene expression, environmental conditions, and interactions between genes.

In summary, the genotype represents the genetic constitution of an organism, while the phenotype represents the observable traits or characteristics resulting from the interaction between the genotype and the environment.