What blood group is said to be world donar?

The correct answer is O negative.

O negative blood type is often called the universal donor because people with O negative blood can safely donate blood to people with any blood type. People with O negative blood are also more likely to be able to donate blood to people with rare blood types. This is because O negative blood does not contain any of the A, B, or Rh (D) antigens that can cause immune reactions in people with other blood types.