Elements P, Q, R, S have 6, 11, 15, 17 electrons respectively, therefore,

This question is asking which of the given options is correct based on the number of electrons in elements P, Q, R, and S. P has 6 electrons, Q has 11 electrons, R has 15 electrons, and S has 17 electrons.

Based on the number of electrons, we can determine the type of bond that each element is likely to form. Elements with similar electronegativity tend to form covalent bonds where they share electrons to achieve a stable octet. Elements with a large difference in electronegativity tend to form ionic or electrovalent bonds where one element donates an electron to the other to achieve a stable octet.

Element P has 6 electrons, so it needs 2 more electrons to achieve a stable octet. Element R has 15 electrons, so it needs to lose 1 electron to achieve a stable octet. Therefore, P and R are likely to form an electrovalent bond.

Element Q has 11 electrons, and element S has 17 electrons. They are both non-metals and have similar electronegativity, so they are likely to form a covalent bond by sharing electrons to achieve a stable octet. Therefore, option B is incorrect.

Option C is incorrect because R is likely to form an electrovalent bond with P, not with S.

Option D is correct because Q is likely to form an electrovalent bond with S due to their large difference in electronegativity. Q has 11 electrons and needs to gain 1 electron to achieve a stable octet, while S has 17 electrons and needs to lose 1 electron to achieve a stable octet. Therefore, option D is the correct answer.

In summary, based on the number of electrons in elements P, Q, R, and S, we can predict which type of bond they are likely to form. P and R are likely to form an electrovalent bond, while Q and S are likely to form an electrovalent bond. Therefore, option D is the correct answer.