Detailed Instructions: 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.  
See one example below:
Problem: Sentence: Namibia conducts a census every ten years. After independence the first Population and Housing Census was carried out in 1991, further rounds followed in 2001 and 2011. The data collection method is to count every person resident in Namibia on the census reference night, wherever they happen to be. This is called the de facto method. For enumeration purposes the country is demarcated into 4,042 enumeration areas. These areas do not overlap with constituency boundaries to get reliable data for election purposes as well. 
Question: How often does Namibia conduct a census?
Solution: every ten years
Explanation: Census is generally conducted every ten years in most countries like Namibia.

Problem: Sentence: The City Parliament (de: Stadtrat, fr: Conseil de ville) holds legislative power. It is made up of 80 members, with elections held every four years. The City Parliament decrees regulations and by-laws that are executed by the City Council and the administration. The delegates are selected by means of a system of proportional representation. 
Question: How often are elections held for the City Parliament?
Solution:
every four years.