You will be given a definition of a task first, then some input of the task.
This task is about creating an unanswerable question based on a given passage. Construct a question that looks relevant to the given context but is unanswerable. Following are a few suggestions about how to create unanswerable questions:
(i) create questions which require satisfying a constraint that is not mentioned in the passage
(ii) create questions which require information beyond what is provided in the passage in order to answer
(iii) replace an existing entity, number, date mentioned in the passage with other entity, number, date and use it in the question
(iv) create a question which is answerable from the passage and then replace one or two words by their antonyms or insert/remove negation words to make it unanswerable.

Passage: For decades, it was the official policy of the Soviet Union to deny the existence of the secret protocol to the SovietGerman Pact. At the behest of Mikhail Gorbachev, Alexander Nikolaevich Yakovlev headed a commission investigating the existence of such a protocol. In December 1989, the commission concluded that the protocol had existed and revealed its findings to the Congress of People's Deputies of the Soviet Union. As a result, the Congress passed the declaration confirming the existence of the secret protocols, condemning and denouncing them. Both successor-states of the pact parties have declared the secret protocols to be invalid from the moment they were signed. The Federal Republic of Germany declared this on September 1, 1989 and the Soviet Union on December 24, 1989, following an examination of the microfilmed copy of the German originals.
Output:
Who rejected an investigation into whether or not the Soviet-German Pact happened?