Context and question: To the south, the Sahara is bounded by the Sahel, a belt of dry tropical savanna with a summer rainy season that extends across Africa from east to west. The southern limit of the Sahara is indicated botanically by the southern limit of Cornulaca monacantha (a drought-tolerant member of the Chenopodiaceae), or northern limit of Cenchrus biflorus, a grass typical of the Sahel. According to climatic criteria, the southern limit of the Sahara corresponds to the 150 mm (5.9 in) isohyet of annual precipitation (this is a long-term average, since precipitation varies annually).
What type of grass is atypical to the Sahel?
Answer: unanswerable
Context and question: Over two centuries after the removal of the capital to Beijing, Nanjing was destined to become the capital of a Ming emperor one more time. After the fall of Beijing to Li Zicheng's rebel forces and then to the Manchu-led Qing dynasty in the spring of 1644, the Ming prince Zhu Yousong was enthroned in Nanjing in June 1644 as the Hongguang Emperor. His short reign was described by later historians as the first reign of the so-called Southern Ming dynasty.
When did Beijing lose to Li Zicheng's rebel forces and the Manchu-led Qing dynasty?
Answer: 1644
Context and question: The effects of some types of mold on infection had been noticed many times over the course of history (see: History of penicillin). In 1928, Alexander Fleming noticed the same effect in a Petri dish, where a number of disease-causing bacteria were killed by a fungus of the genus Penicillium. Fleming postulated that the effect is mediated by an antibacterial compound he named penicillin, and that its antibacterial properties could be exploited for chemotherapy. He initially characterized some of its biological properties, and attempted to use a crude preparation to treat some infections, but he was unable to pursue its further development without the aid of trained chemists.
What did Fleming use to treat a Petri dish?
Answer:
unanswerable