The fundamental frequency of an air column in a pipe closed at one end is 100 Hz. If the same pipe is open at both the ends, the frequencies produced in Hz are
A. `100, 200, 300, 400, "….."`
B. `100, 300, 500, 700, "……"`
C. `200, 300, 400 , 500, "……"`
D. `200, 400, 600, 800, "….."`