When do organs and organ systems begin to develop in human? A. In the sperm cell before fertilization.
B. Before fertilization and after birth.
C. In the egg cell after fertilization.
D. After fertilization and before birth​

D. After fertilization and before birth​

Explanation:

At Six Weeks: The embryo grows to about 1/3- inch (less than one centimetre). The spinal cord, brain, ears and eyes have started to develop. The internal organs (lungs, digestive system, kidneys) begin to appear.

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answer; the tunica intima also called tunica interna, consists of elastic fibers,connective tissue and smooth muscle cells;