In this task, we ask you to write an answer to a question that involves event "frequency", which refers to how often an event is likely to be repeated. For example, "taking showers" typically occurs ~5 times a week, "going to Saturday market" usually happens every few weeks/months, etc. Note that a lot of the questions could have more than one correct answer. We only need a single most-likely answer. Please try to keep your "answer" as simple as possible. Concise and simple "answer" is preferred over those complex and verbose ones.

Q: Sentence: The story then moves forward to 1920 and shows the expedition led by scientist Sir Basil Walden and business man Stanley Preston finding the tomb . 
Question: How often did the scientist lead expeditions?

A: every year.
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Q: Sentence: Pushkin gradually became committed to social reform and emerged as a spokesman for literary radicals. 
Question: How often does Pushkin speak at events?

A: whenever he was asked.
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Q: Sentence: Remembering the "we have some planes" remark, Boston Center guessed that Delta 1989 might also be hijacked. 
Question: How many times a decade do plane hijackings take place?

A:
plane hijackings occur ten times each decade.
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