The greatest common factors of the $$4$$ pairs of numbers are $$2$$, $$5$$, $$3$$, and $$1$$, respectively. 
The greatest common factor is smallest for which of the following pairs of numbers? 

  $$4$$ \& $$18$$ 
  $$5$$ \&~$$25$$ 
  $$6$$ \&~$$33$$ 
  $$8$$ \&~$$35$$ 