Among the given cell organelle, each is responsible for a certain action or function. Cell Nucleus is the brain of the cell and contains all the genetic material of the cell. The main purposes of nucleus include protection of this genetic material and regulation of gene expression. Hence the plans for cell replication, along with plans for other cell activities are in Nucleus. Endoplasmic recticulum is responsible for protein synthesis and metabolism of carbohydrates and lipids, through its two components (smooth and rough endoplasmic recticulum). Mitochondria are the power house of the cell, so named because this organelle is responsible for production of energy (in the form of ATP molecules) in eukaryotic cells. Lysosomes contain degradative enzymes to break down proteins, carbohydrates, etc.
Hence, nucleus is the right answer.
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