Which two of the following functions will perform the addition of two numbers with a minimum number of variables?

def add$($a$,$ b$)$:

return$($a $+$ b$)$

def add$($a$,$ b$)$:

return$($sum$($a$,$ b$))$

def add$($a$,$ b$)$:

return$($sum$(($a$,$ b$)))$

def add$($a$,$ b$)$:

c $=$ a$+$b

return$($c$)$