As a result of the 1905 revolution,
a) political prisoners were released
b) political parties were banned
c) czar nicholas ii was overthrown
d) an elected legislature called the duma was formed

D) an elected legislature called the Duma was formed.

Explanation:

In January 1905, the shooting of striking factory workers in St Petersburg sparked that came to be known as the 1905 Revolution, the first major threat to the tsarist autocracy in the 20th century. For several months, Tsarism has been under attack and there was pressure to adopt radical sociopolitical reforms. the result was that Nicholas Second have to approve for the election of Duma.

b

explanation:

norsemen from northern countries had made earlier journeys