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

[EX Q]: What determines the model of forces?, Context: For certain physical scenarios, it is impossible to model forces as being due to gradient of potentials. This is often due to macrophysical considerations that yield forces as arising from a macroscopic statistical average of microstates. For example, friction is caused by the gradients of numerous electrostatic potentials between the atoms, but manifests as a force model that is independent of any macroscale position vector. Nonconservative forces other than friction include other contact forces, tension, compression, and drag. However, for any sufficiently detailed description, all these forces are the results of conservative ones since each of these macroscopic forces are the net results of the gradients of microscopic potentials.
[EX A]: gradient of potentials

[EX Q]: Why could there be reasonable doubt about the validity of what was stated that she said?, Context: In May 2007, The Daily Telegraph, citing unnamed sources, reported that the Queen was "exasperated and frustrated" by the policies of the British Prime Minister, Tony Blair, that she was concerned the British Armed Forces were overstretched in Iraq and Afghanistan, and that she had raised concerns over rural and countryside issues with Blair. She was, however, said to admire Blair's efforts to achieve peace in Northern Ireland. On 20 March 2008, at the Church of Ireland St Patrick's Cathedral, Armagh, the Queen attended the first Maundy service held outside England and Wales. At the invitation of the Irish President, Mary McAleese, the Queen made the first state visit to the Republic of Ireland by a British monarch in May 2011.
[EX A]: unnamed sources

[EX Q]: Which of the following is most common in roots, chromoplasts or amyloplasts?, Context: The chloroplast membranes sometimes protrude out into the cytoplasm, forming a stromule, or stroma-containing tubule. Stromules are very rare in chloroplasts, and are much more common in other plastids like chromoplasts and amyloplasts in petals and roots, respectively. They may exist to increase the chloroplast's surface area for cross-membrane transport, because they are often branched and tangled with the endoplasmic reticulum. When they were first observed in 1962, some plant biologists dismissed the structures as artifactual, claiming that stromules were just oddly shaped chloroplasts with constricted regions or dividing chloroplasts. However, there is a growing body of evidence that stromules are functional, integral features of plant cell plastids, not merely artifacts.
[EX A]:
amyloplasts