This task is about writing a correct answer for the reading comprehension task. Based on the information provided in a given passage, you should identify the shortest continuous text span from the passage that serves as an answer to the given question. Avoid answers that are incorrect or provides incomplete justification for the question.

Passage: Reflections generally affect polarization. For radio waves, one important reflector is the ionosphere which can change the wave's polarization. Thus for signals received following reflection by the ionosphere (a skywave), a consistent polarization cannot be expected. For line-of-sight communications or ground wave propagation, horizontally or vertically polarized transmissions generally remain in about the same polarization state at the receiving location. Matching the receiving antenna's polarization to that of the transmitter can make a very substantial difference in received signal strength. Question: What reflector can change the waves polarization?
ionosphere

Passage: The Space Age is a period encompassing the activities related to the Space Race, space exploration, space technology, and the cultural developments influenced by these events. The Space Age began with the development of several technologies that culminated with the launch of Sputnik 1 by the Soviet Union. This was the world's first artificial satellite, orbiting the Earth in 98.1 minutes and weighing in at 83 kg. The launch of Sputnik 1 ushered a new era of political, scientific and technological achievements that became known as the Space Age. The Space Age was characterized by rapid development of new technology in a close race mostly between the United States and the Soviet Union. The Space Age brought the first human spaceflight during the Vostok programme and reached its peak with the Apollo program which captured the imagination of much of the world's population. The landing of Apollo 11 was an event watched by over 500 million people around the world and is widely recognized as one of the defining moments of the 20th century. Since then and with the end of the space race due to the dissolution of the Soviet Union, public attention has largely moved to other areas. Question: What did Sputnik 1 usher in?
The Space Age

Passage: All vertebrate brains share a common underlying form, which appears most clearly during early stages of embryonic development. In its earliest form, the brain appears as three swellings at the front end of the neural tube; these swellings eventually become the forebrain, midbrain, and hindbrain (the prosencephalon, mesencephalon, and rhombencephalon, respectively). At the earliest stages of brain development, the three areas are roughly equal in size. In many classes of vertebrates, such as fish and amphibians, the three parts remain similar in size in the adult, but in mammals the forebrain becomes much larger than the other parts, and the midbrain becomes very small. Question: During development, the brain is made up of three swellings at the front of what?

neural tube;