instruction:
In this task, you are given a question and a context passage. You have to answer the question based on the given passage.
question:
Waves contain?, Context: As an electro-magnetic wave travels through the different parts of the antenna system (radio, feed line, antenna, free space) it may encounter differences in impedance (E/H, V/I, etc.). At each interface, depending on the impedance match, some fraction of the wave's energy will reflect back to the source, forming a standing wave in the feed line. The ratio of maximum power to minimum power in the wave can be measured and is called the standing wave ratio (SWR). A SWR of 1:1 is ideal. A SWR of 1.5:1 is considered to be marginally acceptable in low power applications where power loss is more critical, although an SWR as high as 6:1 may still be usable with the right equipment. Minimizing impedance differences at each interface (impedance matching) will reduce SWR and maximize power transfer through each part of the antenna system.
answer:
power

question:
What criteria is used to decide when Armenia was in its heyday?, Context: The first geographical entity that was called Armenia by neighboring peoples (such as by Hecataeus of Miletus and on the Achaemenid Behistun Inscription) was established in the late 6th century BC under the Orontid dynasty within the Achaemenid Persian Empire as part of the latters' territories, and which later became a kingdom. At its zenith (9565 BC), the state extended from the Caucasus all the way to what is now central Turkey, Lebanon, and northern Iran. The imperial reign of Tigranes the Great is thus the span of time during which Armenia itself conquered areas populated by other peoples.
answer:
the span of time during which Armenia itself conquered areas populated by other peoples

question:
What can lead to mammalian color variation?, Context: Mammalian hair, also known as pelage, can vary in color between populations, organisms within a population, and even on the individual organism. Light-dark color variation is common in the mammalian taxa. Sometimes, this color variation is determined by age variation, however, in other cases, it is determined by other factors. Selective pressures, such as ecological interactions with other populations or environmental conditions, often lead to the variation in mammalian coloration. These selective pressures favor certain colors in order to increase survival. Camouflage is thought to be a major selection pressure shaping coloration in mammals, although there is also evidence that sexual selection, communication, and physiological processes may influence the evolution of coloration as well. Camouflage is the most predominant mechanism for color variation, as it aids in the concealment of the organisms from predators or from their prey. Coat color can also be for intraspecies communication such as warning members of their species about predators, indicating health for reproductive purposes, communicating between mother and young, and intimidating predators. Studies have shown that in some cases, differences in female and male coat color could indicate information nutrition and hormone levels, which are important in the mate selection process. One final mechanism for coat color variation is physiological response purposes, such as temperature regulation in tropical or arctic environments. Although much has been observed about color variation, much of the genetic that link coat color to genes is still unknown. The genetic sites where pigmentation genes are found are known to affect phenotype by: 1) altering the spatial distribution of pigmentation of the hairs, and 2) altering the density and distribution of the hairs. Quantitative trait mapping is being used to better understand the distribution of loci responsible for pigmentation variation. However, although the genetic sites are known, there is still much to learn about how these genes are expressed.
answer:
Selective pressures, such as ecological interactions with other populations or environmental conditions, often lead to the variation in mammalian coloration