Consider the elements :
Cs ,Ne , I and F
(a) Identify the element that exhibits only negative oxidation state.
(b) Identify the element that exhibits only postive oxidation state.
(c) Identify the element that exhibits both positive and negative oxidation states.
(d) Identify the element which exhibits neither the negative nor does the positive oxidation state.

Explanation

Cs. It is an alkali metal. Being highly electropositive, it always exhibits positive oxidation state of +1.