instruction:
This task is about reading the given passage and construct a question about the information present in the passage. Construct a question in such a way that (i) it is unambiguous, (ii) it is answerable from the passage, (iii) its answer is unique (iv) its answer is a continuous text span from the paragraph. Avoid creating questions that (i) can be answered correctly without actually understanding the paragraph and (ii) uses same words or phrases given in the passage.
question:
Occupancy sensors to allow operation for whenever someone is within the area being scanned can control lighting. When motion can no longer be detected, the lights shut off. Passive infrared sensors react to changes in heat, such as the pattern created by a moving person. The control must have an unobstructed view of the building area being scanned. Doors, partitions, stairways, etc. will block motion detection and reduce its effectiveness. The best applications for passive infrared occupancy sensors are open spaces with a clear view of the area being scanned. Ultrasonic sensors transmit sound above the range of human hearing and monitor the time it takes for the sound waves to return. A break in the pattern caused by any motion in the area triggers the control. Ultrasonic sensors can see around obstructions and are best for areas with cabinets and shelving, restrooms, and open areas requiring 360-degree coverage. Some occupancy sensors utilize both passive infrared and ultrasonic technology, but are usually more expensive. They can be used to control one lamp, one fixture or many fixtures.
answer:
What sensor controls light with motion sensors? 


question:
In 121 BC, Han forces expelled the Xiongnu from a vast territory spanning the Hexi Corridor to Lop Nur. They repelled a joint Xiongnu-Qiang invasion of this northwestern territory in 111 BC. In that year, the Han court established four new frontier commanderies in this region: Jiuquan, Zhangyi, Dunhuang, and Wuwei. The majority of people on the frontier were soldiers. On occasion, the court forcibly moved peasant farmers to new frontier settlements, along with government-owned slaves and convicts who performed hard labor. The court also encouraged commoners, such as farmers, merchants, landowners, and hired laborers, to voluntarily migrate to the frontier.
answer:
Who made up a majority of the people on the frontier?


question:
In Britain a number of architects are active in the neoclassical style. Two new university Libraries, Quinlan Terry's Maitland Robinson Library at Downing College and ADAM Architecture's Sackler Library illustrate that the approach taken can range from the traditional, in the former case, to the unconventional, in the latter case. Recently, Prince Charles came under controversy for promoting a classically designed development on the land of the former Chelsea Barracks in London. Writing to the Qatari Royal family (who were funding the development through the property development company Qatari Diar) he condemned the accepted modernist plans, instead advocating a classical approach. His appeal was met with success and the plans were withdrawn. A new design by architecture house Dixon Jones is currently being drafted.
answer:

Who has stirred controversy for development and design of Chelsea Barracks?