Option -A)
B) implication,negation is functionally complete because ,
f( p , q) = p-->q = !p OR q
f( !p , q) = p OR q (since we already have NOT we can use it straightaway) .
C) is functionally complete as it is the basic functionally complete set.
D) NAND is a universal gate which can implement NOT,AND,OR . (or even anyother gates,since it is a universal gate)