Best stage to observe shape, size and number of chromosomes is

B. Metaphase- during this phase the chromosome gets more compact or dense and the centromeres of all the chromosomes line up at the equator of the spindle and hence, chromosomes are best visualized during this phase.

C. Prophase- during this phase the DNA and proteins present within the nucleus condenses.

D. Telophase- during this phase the sister chromatids reach the opposite poles of each cell and nuclear vesicles re-form around the chromosomes.

So, the correct answer is 'Metaphase'.