因为$$120$$的因数有：$$1$$、$$2$$、$$3$$、$$4$$、$$5$$、$$6$$、$$8$$、$$10$$、$$12$$、$$15$$、$$20$$、$$24$$、$$30$$、$$40$$、$$60$$、$$120$$，所以一共有$$16$$个因数． 
$$120$$有~\uline{~~~~~~~~~~}~个因数． 
(a) $$16$$ 
(b) $$18$$ 
(c) $$20$$ 
(d) $$24$$ 