A. During M-phase the karyokinesis and cytokinesis occur. During the karyokinesis, the division of chromosomes occurs. After that, the cytoplasm is divided in cytokinesis.

B. During G1​ phase the machinery of proteins required for DNA replication occurs.

C. No division activity occurs during the G0​ phase, It is called the quiescent phase or resting phase.

D. During the G2​ phase, organelles are duplicated and the cell commits for the division.

Hence, the correct answer is 'G2​ phase'.

Organelle Duplication during Cell Cycle

The cell cycle is a series of events that occur in a cell leading to its division and duplication. It can be divided into four phases, namely, G1, S, G2, and M. Each phase has a specific role in the cell cycle. Organelles are specialized structures within a cell that perform specific functions. They also undergo duplication during the cell cycle.

S Phase

The S phase or synthesis phase is the phase in which DNA replication takes place. During this phase, the chromatin fibers are replicated, and the cell prepares for cell division. It is during this phase that most of the organelles duplicate as well. The following organelles duplicate during the S phase:

1. Mitochondria - Mitochondria are organelles that produce energy for the cell. During the S phase, they duplicate to ensure that the daughter cells have enough energy to carry out their functions.

2. Chloroplasts - Chloroplasts are organelles found in plant cells that are responsible for photosynthesis. During the S phase, they duplicate to ensure that the daughter cells have the ability to perform photosynthesis.

3. Peroxisomes - Peroxisomes are organelles that are involved in lipid metabolism and detoxification of harmful substances. They also duplicate during the S phase.

G1, G2, and M Phase

While most of the organelles duplicate during the S phase, some organelles duplicate during the G1, G2, and M phases of the cell cycle. For example:

1. Ribosomes - Ribosomes are organelles involved in protein synthesis. They duplicate during the G1, G2, and M phases.

2. Golgi Apparatus - Golgi apparatus is an organelle involved in the modification and transport of proteins. It duplicates during the G1 and G2 phases.

3. Endoplasmic Reticulum - Endoplasmic reticulum is an organelle involved in the production and transport of proteins and lipids. It duplicates during the G1 and G2 phases.

In conclusion, most of the organelles duplicate during the S phase of the cell cycle. This ensures that the daughter cells have sufficient organelles to carry out their functions. However, some organelles duplicate during other phases of the cell cycle as well. The duplication of organelles is essential for the proper functioning of cells.