Context and question: The production for sulfidic zinc ores produces large amounts of sulfur dioxide and cadmium vapor. Smelter slag and other residues of process also contain significant amounts of heavy metals. About 1.1 million tonnes of metallic zinc and 130 thousand tonnes of lead were mined and smelted in the Belgian towns of La Calamine and Plombieres between 1806 and 1882. The dumps of the past mining operations leach significant amounts of zinc and cadmium, and, as a result, the sediments of the Geul River contain significant amounts of heavy metals. About two thousand years ago emissions of zinc from mining and smelting totaled 10 thousand tonnes a year. After increasing 10-fold from 1850, zinc emissions peaked at 3.4 million tonnes per year in the 1980s and declined to 2.7 million tonnes in the 1990s, although a 2005 study of the Arctic troposphere found that the concentrations there did not reflect the decline. Anthropogenic and natural emissions occur at a ratio of 20 to 1.
What is the ratio that anthropogenic and unnatural emissions occur at?
Answer: unanswerable
Context and question: The central part of the Sahara is hyperarid, with little to no vegetation. The northern and southern reaches of the desert, along with the highlands, have areas of sparse grassland and desert shrub, with trees and taller shrubs in wadis where moisture collects. In the central, hyperarid part, there are many subdivisions of the great desert such as the Tanezrouft, the Tenere, the Libyan Desert, the Eastern Desert, the Nubian Desert and others. These absolute desert regions are characterized by their extreme aridity, and some years can pass without any rainfall.
What are the subdivisions of the northern and southern reaches?
Answer: unanswerable
Context and question: The Hashimiyya movement (a sub-sect of the Kaysanites Shia), led by the Abbasid family, overthrew the Umayyad caliphate. The Abbasids were members of the Hashim clan, rivals of the Umayyads, but the word "Hashimiyya" seems to refer specifically to Abu Hashim, a grandson of Ali and son of Muhammad ibn al-Hanafiyya. According to certain traditions, Abu Hashim died in 717 in Humeima in the house of Muhammad ibn Ali, the head of the Abbasid family, and before dying named Muhammad ibn Ali as his successor. This tradition allowed the Abbasids to rally the supporters of the failed revolt of Mukhtar, who had represented themselves as the supporters of Muhammad ibn al-Hanafiyya.
Who named Muhammad ibn al-Hanafiyya as his successor?
Answer:
unanswerable