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.

While on one hand the Heian period was an unusually long period of peace, it can also be argued that the period weakened Japan economically and led to poverty for all but a tiny few of its inhabitants. The control of rice fields provided a key source of income for families such as the Fujiwara and were a fundamental base for their power. The aristocratic beneficiaries of Heian culture, the Ryōmin (良民 "Good People") numbered about five thousand in a land of perhaps five million. One reason the samurai were able to take power was that the ruling nobility proved incompetent at managing Japan and its provinces. By the year 1000 the government no longer knew how to issue currency and money was gradually disappearing. Instead of a fully realised system of money circulation, rice was the primary unit of exchange. The lack of a solid medium of economic exchange is implicitly illustrated in novels of the time. For instance, messengers were rewarded with useful objects, e.g., an old silk kimono, rather than paid a fee.
What crop was a primary source of income during the Heian period?

The 1973–74 season saw the arrival of Johan Cruyff, who was bought for a world record £920,000 from Ajax. Already an established player with Ajax, Cruyff quickly won over the Barcelona fans when he told the European press that he chose Barcelona over Real Madrid because he could not play for a club associated with Francisco Franco. He further endeared himself when he named his son Jordi, after the local Catalan Saint George. Next to champions like Juan Manuel Asensi, Carles Rexach and Hugo Sotil, he helped the club win the 1973–74 season for the first time since 1960, defeating Real Madrid 5–0 at the Bernabéu along the way. He was crowned European Footballer of the Year in 1973 during his first season with Barcelona (his second Ballon d'Or win; he won his first while playing for Ajax in 1971). Cruyff received this prestigious award a third time (the first player to do so) in 1974, while he was still with Barcelona.
When did Johan Cruyff join Barcelona?

Just as the navigational approach would require programs to loop in order to collect records, the relational approach would require loops to collect information about any one record. Codd's solution to the necessary looping was a set-oriented language, a suggestion that would later spawn the ubiquitous SQL. Using a branch of mathematics known as tuple calculus, he demonstrated that such a system could support all the operations of normal databases (inserting, updating etc.) as well as providing a simple system for finding and returning sets of data in a single operation.

How does a program collect information using a navigational system?