Answer:
They continued to carry out political reforms peacefully, is the right answer.
Step-by-step explanation:
The Warsaw Pact incursion of Czechoslovakia, formally identified as Operation Danube, was a collective incursion of Czechoslovakia by the nations signed the Warsaw Pact. It took place on the midnight of 20–21 August 1968. On this night, Czechoslovakia was attacked approximately by 250,000 troops. But the response of Czechoslovakia to the Soviet invasion came in the form that it continued to carry out political reforms peacefully.