Which of these schemes are not dynamically balanced?

Question

The figures given above show different schemes suggested to transmit continuous rotary motion from axis A to axis B. which of these schemes are not dynamically balanced?

         (a) 1 and 3                      (b) 2 and 3

         (c) 1 and 2                      (d) 1, 2 and 3

Answer 1

A only 2 balance