Question: Extract the answer to the question from the following context. Question: What causes a device to need more power? Context: Some USB devices require more power than is permitted by the specifications for a single port. This is common for external hard and optical disc drives, and generally for devices with motors or lamps. Such devices can use an external power supply, which is allowed by the standard, or use a dual-input USB cable, one input of which is used for power and data transfer, the other solely for power, which makes the device a non-standard USB device. Some USB ports and external hubs can, in practice, supply more power to USB devices than required by the specification but a standard-compliant device may not depend on this.
Answer: motors or lamps

Question: Extract the answer to the question from the following context. Question: What is there a large amount of in New Delhi besides Taxis and Auto Rickshaws? Context: New Delhi has one of India's largest bus transport systems. Buses are operated by the state-owned Delhi Transport Corporation (DTC), which owns largest fleet of compressed natural gas (CNG)-fueled buses in the world. Personal vehicles especially cars also form a major chunk of vehicles plying on New Delhi roads. New Delhi has the highest number of registered cars compared to any other metropolitan city in India. Taxis and Auto Rickshaws also ply on New Delhi roads in large numbers. New Delhi has one of the highest road density in India.
Answer: registered cars

Question: Extract the answer to the question from the following context. Question: What is Rayleigh scattering? Context: In nature, the red color of blood comes from hemoglobin, the iron-containing protein found in the red blood cells of all vertebrates. The red color of the Grand Canyon and other geological features is caused by hematite or red ochre, both forms of iron oxide. It also causes the red color of the planet Mars. The red sky at sunset and sunrise is caused by an optical effect known as Rayleigh scattering, which, when the sun is low or below the horizon, increases the red-wavelength light that reaches the eye. The color of autumn leaves is caused by pigments called anthocyanins, which are produced towards the end of summer, when the green chlorophyll is no longer produced. One to two percent of the human population has red hair; the color is produced by high levels of the reddish pigment pheomelanin (which also accounts for the red color of the lips) and relatively low levels of the dark pigment eumelanin.
Answer:
optical effect