The correct option is D Si
The valency of Cl atom is 1 and since X combines with 4 atoms of Cl and forms XCl4, it shows that the element X has valency 4. Hence it is likely to be in group 14 of the periodic table, adding 10 to 4 (valency), we get 14, which is the group number. In the given options, silicon (Si) is a group 14 member.