instruction:
In this task, you are given a question and a context passage. You have to answer the question based on the given passage.
question:
Why do birds possess gizzards?, Context: Like the reptiles, birds are primarily uricotelic, that is, their kidneys extract nitrogenous waste from their bloodstream and excrete it as uric acid instead of urea or ammonia through the ureters into the intestine. Birds do not have a urinary bladder or external urethral opening and (with exception of the ostrich) uric acid is excreted along with feces as a semisolid waste. However, birds such as hummingbirds can be facultatively ammonotelic, excreting most of the nitrogenous wastes as ammonia. They also excrete creatine, rather than creatinine like mammals. This material, as well as the output of the intestines, emerges from the bird's cloaca. The cloaca is a multi-purpose opening: waste is expelled through it, most birds mate by joining cloaca, and females lay eggs from it. In addition, many species of birds regurgitate pellets. Males within Palaeognathae (with the exception of the kiwis), the Anseriformes (with the exception of screamers), and in rudimentary forms in Galliformes (but fully developed in Cracidae) possess a penis, which is never present in Neoaves. The length is thought to be related to sperm competition. When not copulating, it is hidden within the proctodeum compartment within the cloaca, just inside the vent. The digestive system of birds is unique, with a crop for storage and a gizzard that contains swallowed stones for grinding food to compensate for the lack of teeth. Most birds are highly adapted for rapid digestion to aid with flight. Some migratory birds have adapted to use protein from many parts of their bodies, including protein from the intestines, as additional energy during migration.
answer:
contains swallowed stones for grinding food to compensate for the lack of teeth


question:
What is Sand Point at the tip of?, Context: The main coastal towns are, from the west to the north-east, Minehead, Watchet, Burnham-on-Sea, Weston-super-Mare, Clevedon and Portishead. The coastal area between Minehead and the eastern extreme of the administrative county's coastline at Brean Down is known as Bridgwater Bay, and is a National Nature Reserve. North of that, the coast forms Weston Bay and Sand Bay whose northern tip, Sand Point, marks the lower limit of the Severn Estuary. In the mid and north of the county the coastline is low as the level wetlands of the levels meet the sea. In the west, the coastline is high and dramatic where the plateau of Exmoor meets the sea, with high cliffs and waterfalls.
answer:
Sand Bay


question:
what is the second type of natural formation mentioned?, Context: On Earth, 99% of glacial ice is contained within vast ice sheets in the polar regions, but glaciers may be found in mountain ranges on every continent except Australia, and on a few high-latitude oceanic islands. Between 35°N and 35°S, glaciers occur only in the Himalayas, Andes, Rocky Mountains, a few high mountains in East Africa, Mexico, New Guinea and on Zard Kuh in Iran. Glaciers cover about 10 percent of Earth's land surface. Continental glaciers cover nearly 13,000,000 km2 (5×10^6 sq mi) or about 98 percent of Antarctica's 13,200,000 km2 (5.1×10^6 sq mi), with an average thickness of 2,100 m (7,000 ft). Greenland and Patagonia also have huge expanses of continental glaciers.
answer:

vast ice sheets