Which two important things happened on 27 February?

Correct answer: Attack on police headquarters and formation of the Petrograd Soviet

On 27 February 1917, the revolutionary crisis in Petrograd reached an important turning point. Demonstrators and soldiers attacked or took control of important state facilities, including the police headquarters, weakening the old machinery of repression. On the same day, representatives of workers and soldiers formed the Petrograd Soviet, creating a new centre of political authority. Therefore, option B is correct. The Treaty of Brest-Litovsk was signed later, in 1918, and the USSR was formed in 1922. The Tsar’s coronation and a military victory did not occur on this date. The Comintern and Cheka also belong to later developments, so the other options are chronologically incorrect.