Parantheses mean present of a subgroup or a group of polyatomic ions in a chemical reaction.
<u>Explanation:</u>
In a chemical reaction, sometimes, a compound may be composed of group of polyatomic ions with other ions. Some of the polyatomic ions are sulfate, carbonate, nitrate, hydroxide, bicarbonate, ammonia etc.
So these polyatomic ions are formed by combining two or more elements. Thus, if the number of polyatomic ions in a compound is more than one, then we use parathesis and write those polyatomic ions in it and write the number of polyatomic ions present in the compound as subscript of the parathesis.
For example, Fe₂(SO₄)₃
So here SO₄ is a polyatomic ion and in the compound 3 atoms of SO₄ is required to neutralize the compound and thus paranthesis is used. Thus, parantheses mean present of a subgroup or a group of polyatomic ions in a chemical reaction.
When you inhale, air passes through the nasal cavity. There, mucus and hairs clean the air from most foreign particles before entering the body. Then, the air passes from the nasal cavity to the pharynx. After the pharynx, it passes through the larynx reaching the trachea. After passing through the trachea, the air reaches the bronchi, and after the bronchi, the bronchioles that branch off the bronchi. From the bronchioles, the air reaches the alveoli that is when gas exchange happens. O2 enters and CO2 leaves.
A requires oxygen
The reason is that fermentation does not always need oxygen.
Answer: A dune is a mound of sand formed by the wind, usually along the beach or in a desert. Dunes can also be formed by strong currents beneath the water.
