a) Give reason:
i) Fluorine exhibits only one oxidation state whereas other halogens exhibit multiple oxidation states. 
ii) Most of the reactions with fluorine are exothermic.

Explanation

i)Fluorine exhibits only one oxidation states whereas other halogens exhibit multiple oxidation states due to absence of d orbitals in the valence shell 
ii) Most of the reactions with fluorine are exothermic due to small size and strong bond formed by fluorine with other elements.