Question

one of the first things vladimir i did after he became the ruler of kiev was to
force the population to submit to his authoritarian rule.
make orthodox christianity the state religion.
isolate kiev so that trade virtually stopped.
create a strong military for kievs defense.

Explanation:

Vladimir I, also known as Vladimir the Great, is a significant figure in Kievan Rus' history. In 988, he chose Orthodox Christianity as the state religion of Kievan Rus'. This decision had a profound impact on the culture, society, and identity of the region. It was not about forcing an authoritarian rule in the described way. Kievan Rus' was an important trading hub, and he did not isolate it to stop trade. While military was important, the key early religious move was adopting Orthodox Christianity as the state religion.

Answer:

make Orthodox Christianity the state religion.