Which of the following statements is true? part of the bohr model proposed that electrons in the hydrogen atom are located in "stationary states" or particular orbits around the nucleus. an orbital is the volume in which we are most likely to find an electron. the uncertainty principle states that we can never know both the exact location and speed of an electron. the emission spectrum of a particular element is always the same and can be used to identify the element. all of the above are true.

All of the above are True

All of the above are true.

Explanation:

According to Bohr model, the electrons orbit around the nucleus in particular orbits. These orbits have fixed energy. when electrons jump from one orbit to another, they lose or gain fixed energy. So, the first statement is true. The emission spectrum of a particular element is always same and can be used to identify element. This is used to identify the composition of stars from their spectrum. Hence, the last statement is also true.

The orbital is a region around the nucleus in an atom where is high probability for an atom to exist. According to uncertainty principle, the exact location and speed of an electron cannot be found. So, third and fourth statement are true.

Thus, the correct option is- All of the above are true.

estuaries are the partially enclosed coastal bodies of brackish water formed at the mouth of sea where river meets an ocean. it is a transition zone between river and sea water so estuaries are influenced to both marine environment such as tides, waves and to riverine such as flow of fresh water and sediments. the mixing of sea and fresh water provide high level of nutrients, making estuaries a high product habitats.

many estuaries suffers degradation from a variety of human activities like erosion from deforestation, overgrazing, overfishing, drainage and eutrophication.

so from the above statement answers will be

1. false as estuaries are formed due to both brackish and freshwater.

2.true, due to high productivity estuaries are breeding ground for many marine species.

3. direct and indirect activities of man that contribute to pollution and deposition of sediments.