Which pair shows compounds with the same radical? a. naoh and nacl b. ba(oh)2 and ba(no3)2 c. al(oh)3 and naoh d. ba(no3)2 and al(oh)3

The correct option is C.
In chemistry, a radical is defined as an atom, ion or molecule that possess an unpaired valence electron. Generally, radicals are highly reactive chemically. Examples of radicals are hydroxyl, hypochlorite, nitrate, carbonate, oxalate, permanganate, etc. Free radicals combine with one another or with single atoms to produce neutral substances. In the question given above, the two compounds given in option C have the same type of radical, which is hydroxyl radical. 

A radical also kinown as a polyatomic ion is a group of atoms that form a unit that is most time negatively charged and attach to a positive ion.  

The answer therefore is C Both have the OH radical