A. Li, Be, Al and D
B. Na, P, O and Cl
C. B, C, N, and O
D. Na, Mg, S and Ar

Correct Answer:

Option D – Na, Mg, S and Ar


Na, Mg, S and Ar are the set of elements that belong to third period of the periodic table. Option A, B, C have elements which belong to the other period in the periodic table included in them.

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