निम्नलिखित में से कौन सी स्थिति माइक्रोसिटिक हाइपोक्रोमिक एनीमिया का सबसे आम कारण है?

Which blood group is known as the Universal Donor?

Antibodies related to the ABO blood group system are found in the:

If a patient needs an emergency blood transfusion and their blood group is unknown, which blood type should be given?