For groups 13 through 18, the number of valence electrons is equal to the group number

a. minus 10
b. minus the period number
c. plus 1
d. plus the period number ​

a. minus 10

Explanation:

An element in group 13 = Boron ,valence electrons = 3 , therefore, valence electrons in group 13 = group no. -10

An element in group 18 = Neon, valence electrons = 8 , therefore, valence electrons in group 18 = group no. - 10