instruction:
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.
question:
Passage: Indian astronomer and mathematician Aryabhata (476-550), in his Aryabhatiya (499) introduced a number of trigonometric functions (including sine, versine, cosine and inverse sine), trigonometric tables, and techniques and algorithms of algebra. In 628 AD, Brahmagupta suggested that gravity was a force of attraction. He also lucidly explained the use of zero as both a placeholder and a decimal digit, along with the Hindu-Arabic numeral system now used universally throughout the world. Arabic translations of the two astronomers' texts were soon available in the Islamic world, introducing what would become Arabic numerals to the Islamic World by the 9th century. During the 14th16th centuries, the Kerala school of astronomy and mathematics made significant advances in astronomy and especially mathematics, including fields such as trigonometry and analysis. In particular, Madhava of Sangamagrama is considered the "founder of mathematical analysis". Question: What did Brahmagupta use the number zero for?
answer:
a placeholder and a decimal digit

question:
Passage: Most of the state has a humid subtropical climate, with the exception of some of the higher elevations in the Appalachians, which are classified as having a mountain temperate climate or a humid continental climate due to cooler temperatures. The Gulf of Mexico is the dominant factor in the climate of Tennessee, with winds from the south being responsible for most of the state's annual precipitation. Generally, the state has hot summers and mild to cool winters with generous precipitation throughout the year, with highest average monthly precipitation generally in the winter and spring months, between December and April. The driest months, on average, are August to October. On average the state receives 50 inches (130 cm) of precipitation annually. Snowfall ranges from 5 inches (13 cm) in West Tennessee to over 16 inches (41 cm) in the higher mountains in East Tennessee. Question: What is the most common climate across Tennessee?
answer:
humid subtropical

question:
Passage: The gut is generally an almost straight tube supported by the mesenteries (vertical partitions within segments), and ends with the anus on the underside of the pygidium. However, in members of the tube-dwelling family Siboglinidae the gut is blocked by a swollen lining that houses symbiotic bacteria, which can make up 15% of the worms' total weight. The bacteria convert inorganic matter such as hydrogen sulfide and carbon dioxide from hydrothermal vents, or methane from seeps to organic matter that feeds themselves and their hosts, while the worms extend their palps into the gas flows to absorb the gases needed by the bacteria. Question: How much of a Siboglinidae's weight is symbiotic bacteria?
answer:
15%