VERY URGENT PLZ HELP

If f(x)=[tex]x^{2}[/tex]−x , then evaluate f(a−4) .




A) [tex]a^{2}[/tex]−9a+20


B) [tex]a^{2}[/tex]−9a+12


C) [tex]a^{2}[/tex]−a−20


D)[tex]a^{2}[/tex]−4