Answer:
14 billion years
Explanation:
Because the percentage of parent isotope remaining decreases by 50% at 14 billion years.
The answer is A because it is the best answer that the students gave.
The thyroid is a butterfly-shaped gland that lies in front of the windpipe (trachea), just below the voice box. The parathyroid glands are four tiny glands located behind the thyroid gland. The parathyroid glands produce a substance (parathyroid hormone) that helps control the amount of calcium in the blood.
Also, it is made up of water and contains enzymes, organelles, salts and various organic molecules. Furthermore, cytoplasm functions by supporting and suspending organelles and cellular molecules. However, example of cytoplasm includes: mitochondria, ribosomes while nucleus is an example of non-example of cytoplasm.
