You will be given a definition of a task first, then some input of the task.
This task is about reading the given passage and construct a question about the information present in the passage. Construct a question in such a way that (i) it is unambiguous, (ii) it is answerable from the passage, (iii) its answer is unique (iv) its answer is a continuous text span from the paragraph. Avoid creating questions that (i) can be answered correctly without actually understanding the paragraph and (ii) uses same words or phrases given in the passage.

During the Perestroika era, The Law on the Status of the Estonian Language was adopted in January 1989. The collapse of the Soviet Union led to the restoration of Republic of Estonia's independence. Estonian went back to being the only state language in Estonia which in practice meant that use of Estonian was promoted while the use of Russian was discouraged.
Output:
What historical event once again freed Estonia?