4. A string with two ends fixed has 12 Hz, 30 Hz, 33 Hz, and 45 Hz as harmonic frequencies. Which of the following is a possible fundamental frequency (first harmonic) of the string?
(A) 2 Hz
(B) 3 Hz
(C) 5 Hz
(D) 12 Hz
(E) 18 Hz
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統計: 尚無統計資料
統計: 尚無統計資料