Which format was used for movies of the 1910s and 1920s?

Generally speaking the format was of black and white and silent format. However by the last quarter of the 1920´s decade sound was introduced giving way to the concept of "musical"

the 22nd united states congress

peasants’ war, (1524–25) peasant uprising in germany inspired by changes brought by the reformation, peasants in western and southern germany invoked   divine law to demand agrarian rights and freedom from oppression by nobles and landlords. as the uprising spread, some peasant groups organized armies. although the revolt was supported huldrych zwingli and thomas müntzerits condemnation by martain luther contributed to its defeat, principally by the army of the swabian league. some 100,000 peasants were killed. reprisals and increased restrictions discouraged further attempts to improve the peasants’ plight.

i think it would be " a" i might be wrong tho