A closed organ pipe has fundamental frequency $100 \mathrm{~Hz}$. What frequencies will be produced if its other end is also opened?
(A) $200,400,600,800 \ldots \ldots$
(B) $200,300,400,500 \ldots \ldots$
(C) $100,300,500,700 \ldots \ldots$
(D) $100,200,300,400 \ldots \ldots$