The correct answer is option 3 - 1, 2 and 3.

Explanation:

1. In Jallianwala Bagh, troops opened fire upon an unarmed crowd: This statement is correct. On April 13, 1919, British troops under the command of General Dyer opened fire on a crowd of unarmed Indians who had gathered in Jallianwala Bagh in Amritsar, Punjab.

2. The troops were under the command of General Dyer: This statement is correct. General Dyer was in command of the troops that fired upon the crowd. He personally ordered the soldiers to open fire on the crowd.

3. The troops did not issue any warning to the people before opening fire: This statement is correct. The troops did not issue any warning to the crowd and without any provocation, they began firing on the people. The firing continued for about 10 minutes, resulting in the death of hundreds of people and injuring many more.

Therefore, all three statements are correct, and the correct answer is option 3.