Atom X has 17 protons. How many electrons are in its valence shell (outermost energy level)? A. 7
B.3
C.5
D.10

Atom C has 17 protons, and since it is stated in the question that it's an atom, not an ion so it will have same number of electrons as protons, so that the atom will be electrically neutral.

now,

since, last shell is M shell... So, number of electrons in its valence shell (outermost energy level) is 7 electrons

answer: c. two haploid cells

explanation:

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.