In this task, you are given a question and a context passage. You have to answer the question based on the given passage.

Input: Consider Input: What does every plane have?, Context: Grey-box testing (American spelling: gray-box testing) involves having knowledge of internal data structures and algorithms for purposes of designing tests, while executing those tests at the user, or black-box level. The tester is not required to have full access to the software's source code.[not in citation given] Manipulating input data and formatting output do not qualify as grey-box, because the input and output are clearly outside of the "black box" that we are calling the system under test. This distinction is particularly important when conducting integration testing between two modules of code written by two different developers, where only the interfaces are exposed for test.

Output: black box


Input: Consider Input: Who practices SODIS?, Context: Solar water disinfection (SODIS) involves exposing water-filled plastic polyethylene terephthalate (PET) bottles to sunlight for several hours. Exposure times vary depending on weather and climate from a minimum of six hours to two days during fully overcast conditions. It is recommended by the World Health Organization as a viable method for household water treatment and safe storage. Over two million people in developing countries use this method for their daily drinking water.

Output: Over two million people


Input: Consider Input: Since the 20th century there has been significant population movement to __., Context: A recent addition to the exhibition is the late 13th-century Westminster Retable, England's oldest altarpiece, which was most probably designed for the high altar of the abbey. Although it has been damaged in past centuries, the panel has been expertly cleaned and conserved.
Output: England