Consider the following statements:

1). Critical or whirling speed of the shaft is the speed at which it tends to vibrate violently in the transverse direction 2). To find the natural frequency of a shaft carrying several loads, the energy method gives approximate results 3). Dunkerley's method gives accurate results of the natural frequency of a shaft carrying several loads Which of these statements is/are correct?

(a) 1 only

(b) 2 and 3

(c) 1 and 3

(d) 1,2 , and 3 .