The correct option is B The British troops warned the people to leave the area before firing.
General Dyer with his troops fired at the unarmed crowd at the Jallianwala Bagh on 13 April 1919. He sealed off the only exit and commanded his troops to open fire on the people without giving them a warning. The shooting continued for ten minutes and stopped only when they ran out of ammunition. 379 people were dead, and 1200 were brutally wounded in the firing.