The element which never shows the positive oxidation state is:
(A) F
(B) Cl
(C) Br
(D) I

Hint: Oxidation state of an element is nothing but oxidation number of an element. It is nothing but the number of electrons lost or gained by an element to form a bond with other atoms. Some elements show a positive oxidation number and some elements show a negative oxidation number.

Complete step by step solution:
-The oxidation number of an element is positive means the element loses the electrons.
-The oxidation number of an element is negative means the element gains the electrons.
-The oxidation number of an element is going to depend on the electronegativity of the element also.
-Electron accepting capability of an element is called electronegativity.
-Now we have to find which element does not show a positive oxidation number.
-The elements in the given options are Fluorine (F), Chlorine (Cl), Bromine (Br) and Iodine (I).
-All the given elements belong to halogens.
-The electronegativity values of Fluorine (F), Chlorine (Cl), Bromine (Br) and Iodine (I) are 4.0, 3.0, 2.8 and 2.5 respectively.
-Among the given options Fluorine has the highest electronegativity and fluorine the element has high electronegativity value when compared to the remaining elements in the periodic table.
-The oxidation state of fluorine is -1 always.
-Then fluorine won’t show a positive oxidation number.

So, the correct option is A.

Note: Fluorine always shows the highest electronegativity because of the small size and it accepts electrons very easily. After accepting an electron from other elements, fluorine will get an octet electronic configuration. So, fluorine always shows a negative (-1) oxidation state.