TASK DEFINITION: This task is about writing a correct answer for the reading comprehension task. Based on the information provided in a given passage, you should identify the shortest continuous text span from the passage that serves as an answer to the given question. Avoid answers that are incorrect or provides incomplete justification for the question.
PROBLEM: Passage: Nanjing borders Yangzhou to the northeast, one town downstream when following the north bank of the Yangtze, Zhenjiang to the east, one town downstream when following the south bank of the Yangtze, and Changzhou to the southeast. On its western boundary is Anhui province, where Nanjing borders five prefecture-level cities, Chuzhou to the northwest, Wuhu, Chaohu and Maanshan to the west and Xuancheng to the southwest. Question: What city is northeast of Nanjing?

SOLUTION: Yangzhou

PROBLEM: Passage: In Chapter II, Darwin specifies that the distinction between species and varieties is arbitrary, with experts disagreeing and changing their decisions when new forms were found. He concludes that "a well-marked variety may be justly called an incipient species" and that "species are only strongly marked and permanent varieties". He argues for the ubiquity of variation in nature. Historians have noted that naturalists had long been aware that the individuals of a species differed from one another, but had generally considered such variations to be limited and unimportant deviations from the archetype of each species, that archetype being a fixed ideal in the mind of God. Darwin and Wallace made variation among individuals of the same species central to understanding the natural world. Question: What does Darwin believe about the differences between species and varieties?

SOLUTION: is arbitrary

PROBLEM: Passage: Dogs are highly variable in height and weight. The smallest known adult dog was a Yorkshire Terrier, that stood only 6.3 cm (2.5 in) at the shoulder, 9.5 cm (3.7 in) in length along the head-and-body, and weighed only 113 grams (4.0 oz). The largest known dog was an English Mastiff which weighed 155.6 kg (343 lb) and was 250 cm (98 in) from the snout to the tail. The tallest dog is a Great Dane that stands 106.7 cm (42.0 in) at the shoulder. Question: Dogs show an extreme range in what two characteristics?

SOLUTION:
height and weight.