During the restoration, milton was

appointed latin secretary in cromwell's office of foreign affairs
imprisoned because of his connection to the failed commonwealth
traveling and studying in italy where he meet others scholars of the period
publishing political tracts in defense of the execution of charles i

The best and most correct answer among the choices provided by the question is the second choice "imprisoned because of his connection to the failed Commonwealth" 

John Milton was an English poet, polemicist, man of letters, and civil servant for the Commonwealth of England under Oliver Cromwell.

I hope my answer has come to your help. God bless and have a nice day ahead!