TASK DEFINITION: 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.
PROBLEM: This means that in a closed system of particles, there are no internal forces that are unbalanced. That is, the action-reaction force shared between any two objects in a closed system will not cause the center of mass of the system to accelerate. The constituent objects only accelerate with respect to each other, the system itself remains unaccelerated. Alternatively, if an external force acts on the system, then the center of mass will experience an acceleration proportional to the magnitude of the external force divided by the mass of the system.:19-1

SOLUTION: What experiences acceleration when external force is applied to a system?

PROBLEM: Theoretical analyses show that detours that increase flight distance by up to 20% will often be adaptive on aerodynamic grounds - a bird that loads itself with food to cross a long barrier flies less efficiently. However some species show circuitous migratory routes that reflect historical range expansions and are far from optimal in ecological terms. An example is the migration of continental populations of Swainson's thrush Catharus ustulatus, which fly far east across North America before turning south via Florida to reach northern South America; this route is believed to be the consequence of a range expansion that occurred about 10,000 years ago. Detours may also be caused by differential wind conditions, predation risk, or other factors.

SOLUTION: What percentage increase in flight distance will often be adaptive?

PROBLEM: The largest parks in the central area of London are three of the eight Royal Parks, namely Hyde Park and its neighbour Kensington Gardens in the west, and Regent's Park to the north. Hyde Park in particular is popular for sports and sometimes hosts open-air concerts. Regent's Park contains London Zoo, the world's oldest scientific zoo, and is near the tourist attraction of Madame Tussauds Wax Museum. Primrose Hill in the northern part of Regent's Park at 256 feet (78 m) is a popular spot to view the city skyline.

SOLUTION:
How many royal parks are located in the center of London?