The best stage at which the total number of chromosomes can be counted in any species is

The correct option is Metaphase.

To understand why metaphase is the best stage for counting chromosomes, let us examine the structural changes chromosomes undergo during the different stages of cell division (mitosis):

1. Condensation and Alignment:
During prophase, chromatin fibers start to condense, but they remain relatively long and thin. By the time the cell enters metaphase, the chromosomes reach their maximum state of condensation and compaction. This makes them thick, short, and highly distinct under a light microscope.

2. Equatorial Plate Arrangement:
In metaphase, the spindle fibers attach to the kinetochores of the chromosomes and align them along the equatorial plane (metaphase plate) of the cell. This orderly arrangement ensures that the chromosomes are spread out and do not overlap significantly, which is essential for accurate counting and karyotyping.

3. Comparison with other phases:
- Late prophase: Chromosomes are still in the process of condensing and are not yet aligned systematically.
- Late anaphase: Sister chromatids have already separated and are moving toward opposite poles, which complicates counting the diploid set.
- Telophase: Chromosomes reach the poles and begin to decondense back into a diffuse chromatin network, losing their distinct individuality.

Therefore, because of maximum chromosomal condensation and clear alignment at the equatorial plate, Metaphase is the optimal stage to count the total number of chromosomes and study their morphology.