In this task, you're given passages that contain mentions of a time duration related quesry and we are supposed to write 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 answers. 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: Birds need to alter their metabolism in order to meet the demands of migration. The storage of energy through the accumulation of fat and the control of sleep in nocturnal migrants require special physiological adaptations. In addition, the feathers of a bird suffer from wear-and-tear and require to be molted. The timing of this molt - usually once a year but sometimes twice - varies with some species molting prior to moving to their winter grounds and others molting prior to returning to their breeding grounds. Apart from physiological adaptations, migration sometimes requires behavioural changes such as flying in flocks to reduce the energy used in migration or the risk of predation. 
Question: How often do birds molt?
[A]: usually once a year


[Q]: Sentence: During the period from 1993 to 2011, FBI agents fired their weapons on 289 occasions; FBI internal reviews found the shots justified in all but 5 cases, in none of the 5 cases were people wounded. Samuel Walker, a professor of criminal justice at the University of Nebraska Omaha said the number of shots found to be unjustified was "suspiciously low." In the same time period, the FBI wounded 150 people, 70 of whom died; the FBI found all 150 shootings to be justified. Likewise, during the period from 2011 to the present, all shootings by FBI agents have been found to be justified by internal investigation. In a 2002 case in Maryland, an innocent man was shot, and later paid $1.3 million by the FBI after agents mistook him for a bank robber; the internal investigation found that the shooting was justified, based on the man's actions. 
Question: How many times were FBI shots not justified?
[A]: 5 cases


[Q]: Sentence: On 2 March 1979, the GPC announced the separation of government and revolution, the latter being represented by new Revolutionary Committees, who operated in tandem with the People's Committees in schools, universities, unions, the police force and the military. Dominated by revolutionary zealots, the Revolutionary Committees were led by Mohammad Maghgoub and a Central Coordinating Office, and met with Gaddafi annually. Publishing a weekly magazine The Green March (al-Zahf al-Akhdar), in October 1980 they took control of the press. Responsible for perpetuating revolutionary fervour, they performed ideological surveillance, later adopting a significant security role, making arrests and putting people on trial according to the "law of the revolution" (qanun al-thawra). With no legal code or safeguards, the administration of revolutionary justice was largely arbitrary and resulted in widespread abuses and the suppression of civil liberties: the "Green Terror." 
Question: How often was al-Zahf al-Akhdar published?
[A]:
weekly