Problem: Sahara:

The Sahara is the world's largest low-latitude hot desert. The area is located in the horse latitudes under the subtropical ridge, a significant belt of semi-permanent subtropical warm-core high pressure where the air from upper levels of the troposphere tends to sink towards the ground. This steady descending airflow causes a warming and a drying effect in the upper troposphere. The sinking air prevents evaporating water from rising and, therefore, prevents the adiabatic cooling, which makes cloud formation extremely difficult to nearly impossible.

Why is cloud formation so common?
---
A: unanswerable

Problem: Many ancient civilizations alloyed metals for purely aesthetic purposes. In ancient Egypt and Mycenae, gold was often alloyed with copper to produce red-gold, or iron to produce a bright burgundy-gold. Gold was often found alloyed with silver or other metals to produce various types of colored gold. These metals were also used to strengthen each other, for more practical purposes. Copper was often added to silver to make sterling silver, increasing its strength for use in dishes, silverware, and other practical items. Quite often, precious metals were alloyed with less valuable substances as a means to deceive buyers. Around 250 BC, Archimedes was commissioned by the king to find a way to check the purity of the gold in a crown, leading to the famous bath-house shouting of "Eureka!" upon the discovery of Archimedes' principle.
Softer silver was used for what practical items?
---
Answer: unanswerable

Q: What is a question about this article? If the question is unanswerable, say "unanswerable".
During the summer growing season, phosphate is at a high level. It has a vital role in the breakdown of the sugars manufactured by chlorophyll. But in the fall, phosphate, along with the other chemicals and nutrients, moves out of the leaf into the stem of the plant. When this happens, the sugar-breakdown process changes, leading to the production of anthocyanin pigments. The brighter the light during this period, the greater the production of anthocyanins and the more brilliant the resulting color display. When the days of autumn are bright and cool, and the nights are chilly but not freezing, the brightest colorations usually develop.
At which period of the year are phosphates high?
A: the summer growing season

Context and question: In 1887, the British Empire celebrated Victoria's Golden Jubilee. Victoria marked the fiftieth anniversary of her accession on 20 June with a banquet to which 50 kings and princes were invited. The following day, she participated in a procession and attended a thanksgiving service in Westminster Abbey. By this time, Victoria was once again extremely popular. Two days later on 23 June, she engaged two Indian Muslims as waiters, one of whom was Abdul Karim. He was soon promoted to "Munshi": teaching her Hindustani, and acting as a clerk. Her family and retainers were appalled, and accused Abdul Karim of spying for the Muslim Patriotic League, and biasing the Queen against the Hindus. Equerry Frederick Ponsonby (the son of Sir Henry) discovered that the Munshi had lied about his parentage, and reported to Lord Elgin, Viceroy of India, "the Munshi occupies very much the same position as John Brown used to do." Victoria dismissed their complaints as racial prejudice. Abdul Karim remained in her service until he returned to India with a pension on her death.
How many kings and princes were invited to the Golden Jubilee?
Answer: 50

Question: As a teenager, he was greatly troubled by the Metaphysics of Aristotle, which he could not understand until he read al-Farabi's commentary on the work. For the next year and a half, he studied philosophy, in which he encountered greater obstacles. In such moments of baffled inquiry, he would leave his books, perform the requisite ablutions, then go to the mosque, and continue in prayer till light broke on his difficulties. Deep into the night, he would continue his studies, and even in his dreams problems would pursue him and work out their solution. Forty times, it is said, he read through the Metaphysics of Aristotle, till the words were imprinted on his memory; but their meaning was hopelessly obscure, until one day they found illumination, from the little commentary by Farabi, which he bought at a bookstall for the small sum of three dirhams. So great was his joy at the discovery, made with the help of a work from which he had expected only mystery, that he hastened to return thanks to God, and bestowed alms upon the poor.
Is there an answer to this question: What text could Avicenna understand?

Answer: unanswerable

Q: What is a question about this article? If the question is unanswerable, say "unanswerable".
As in most of eastern China the ethnic makeup of Nanjing is predominantly Han nationality (98.56 percent), with 50 other minority nationalities. In 1999, 77,394 residents belonged to minority nationalities, among which the vast majority (64,832) were Hui nationalities, contributing 83.76 percent to the minority population. The second and third largest minority groups were Manchu (2,311) and Zhuang (533) nationalities. Most of the minority nationalities resided in Jianye District, comprising 9.13 percent of the district's population.
What is the overwhelming ethnic majority in Nanjing?
A:
Han nationality