Respuesta :
Answer:
Option (D).
Explanation:
The modern periodic table is used to study the physical and chemical properties of each element. The modern periodic table shows periodicity in the elements.
The study of the element can be done down the group and along the period. As we go down the group in the periodic table, the number of valance shell increases by one unit but the number of electron in the outermost shell remains same.
Thus, the correct answer is option (D).