Choose the incorrect statement.

• A
  Fleming's right-hand rule is a simple rule to know the direction of induced current.
• B
  The right-hand thumb rule is used to find the direction of magnetic fields due to current-carrying conductors.
• C
  The difference between the direct and alternating currents is that the direct current always flows in one direction,whereas the alternating current reverses its direction periodically.
• D
  In India,the $AC$ changes direction after every $\frac{1}{50}$ second.