The correct answer is option 
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The is an ion made up of two atoms nitrogen and hydrogen.
The polyatomic ions are those ions, which are formed by the binding of the two or more elements, which has a charge and act as an ion. As all others are formed by a single atom, they are not polyatomic, only is formed by two atoms, hence, it is an polyatomic ion.
In capillaries, the outer tunics of smooth muscle cells are absent and only the endothelium is present. Capillaries are often invested in pericapillary contractile cells called pericytes. The layer of endothelial cells is a type of epithelium and is bounded at its outer surface by a basement membrane.
Answer:well this is what i know
Photosynthesis is the process by which plants convert energy from the sun. It is the process that allows plants to create organic molecules that they use as fuel. Here is how it works. The molecules of chlorophyll contained in the chloroplasts absorb energy in the form of light from the sun.
Explanation: So plants get the energy from the sun which is why the sun is important during photosynthesis .
When studying a complex biological phenomenon, it is required to look at the workings of the various systems associated with it. The research is a top-down approach of getting down to the very detail of the cells and molecules taking part in it. Example, a person finds it difficult to digest milk and vomits it on ingestion. As we go a level down, we identify the systems getting affected by the milk. Then, further down, the cells that take in digesting the milk are identified. The enzymes that break down the substances in the milk are identified. The gene regulation of this enzyme (lactase) is studied to check its regulation. This work of doing a top-down approach to find the signalling pathway within the cells to identify the problem with the working of lactase to digest milk, is a necessary approach.
