The basic living unit of all organisms is the- A. Organ B. Tissue C. Organ System D. Cell

Option D is the correct option

Explanation:

The bodies of all plants and animals are made up of basic units. These basic units are called cells . Cells carry out different life activities like respiration , growth , digestion, excretion etc. All living organisms are made up of cells. Cells are like the bricks of a house. Cells are also called the building blocks of organisms. They are known as the basic structural and functional units of life . They are the smallest unit of life. Cells were discovered by an English Scientist Robert Hooke in 1665 AD . Cells are very small. We cannot see them with our names eyes. We use an instrument called microscope to see them. The shapes of cells vary. However, cells may be oval , round , tabular, branched , cylindrical or irregular in shape. Similarly , the size can vary from very small to large. Usually, the diameter of cells ranges from 0.5 micron to 151 microns.

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c. orbital shape i hope this is correct