The answer is:
A. 17
The explanation:
first we have to define the oxidation state:
It is the loss of the electrons in the atom of the component , or the amount of the oxidation or the degree of the oxidation of an atom.
and the group 17 consist of Halogens:
1- Fluorine : with atomic number 9 , The oxidation state of it is always -1 but in its diatomic case the oxidation state is zero.
2- chlorine: Cl with atomic number 17 , The oxidation states of it are multiple oxidation states for example -1, +1, 3, 5, and 7.
3- Bromine: Br with atomic number 35 , The oxidation states of it are -1, +1, 3, 4 and 5.
4- Iodine: I with atomic number 53 , The oxidation states of it are oxidation states -1, +1, 5 and 7
5- Astatine: At with atomic number 85, The oxidation states of it are -1, +1, 3, 5 and 7
So this group (17) exhibit both positive and negative oxidation states.
