Question

what were the cheka, which lenin used to deal with those who opposed his rule?
group of mensheviks
secret police force
special army unit
group of radical revolutionaries

Explanation:

The Cheka was established by Lenin as a secret police force. It was used to suppress opposition and maintain the Bolshevik rule. Mensheviks were a political group opposing the Bolsheviks. A special army unit would have a different role than internal security. A group of radical revolutionaries does not fit the Cheka's function as a security - enforcement body.

Answer:

secret police force