Which of the following statement is correct:

1). If a rotor is statically balanced it is always dynamically balanced also 2). If a rotor is dynamically balanced, it must be statically balanced 3). If a rotor is dynamically balanced, it may or may not be statically balanced 4). If a rotor is statically balanced, it may or may not be dynamically balanced

(a) 1 and 2 only

(b) 2 ans 4 only

(c) 2 and 3 only

(d) 1 and 4 only.