Explanation:

Chromosomes are the structures in the cell nucleus that contain genetic information in the form of DNA. Diagrammatic representation of chromosomes is called an idiogram.

Idiogram:
An idiogram is a graphical representation of the chromosomes of an organism. It is a schematic representation of the karyotype and shows the relative size, shape, and banding pattern of each chromosome. An idiogram is created by arranging the chromosomes in pairs according to their size and shape.

Karyotype:
A karyotype is a visual display of an individual's chromosomes. It is a picture of all the chromosomes in an individual's cells arranged in a specific order. Karyotypes are used to identify genetic disorders and to determine the sex of an individual.

Chromosome map:
A chromosome map is a diagram that shows the location of genes on a chromosome. Chromosome maps are used to study the inheritance of genetic traits and to identify the location of disease-causing genes.

Phenogram:
A phenogram is a graphical representation of the similarities and differences between different organisms based on their physical characteristics. Phenograms are used to study evolutionary relationships between different species.

Therefore, the correct answer is option B, idiogram, as it specifically refers to the diagrammatic representation of chromosomes.

Correct option is B)
Karyotype refers to a representation of relative size, shape and number of chromosomes and position of the centromere in a complete set of chromosomes. Karyotypes are species specific and are used to study their phylogenetic relationship. Diagrammatic representation of chromosomal morphology is termed as idiogram which is characteristic of a species or population; option B is correct. A karyotype is mostly, but not always, represented as idiogram; option A is incorrect. Chromosomal map refers to a graphic representation of the relative positions of genes on chromosomes. A chromosomal map is created by using chromosome bands or by recombination frequency, the degree of linkage between genes; option C is incorrect. Phenogram refers to the representation of the range of similarity among taxa, in the form of a branching diagrammatic tree, to show their phylogenetic relationship