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: Returning to the basic concept of current flows in a conductor, consider what happens if a half-wave dipole is not connected to a feed point, but instead shorted out. Electrically this forms a single 1⁄2-wavelength element. But the overall current pattern is the same; the current will be zero at the two ends, and reach a maximum in the center. Thus signals near the design frequency will continue to create a standing wave pattern. Any varying electrical current, like the standing wave in the element, will radiate a signal. In this case, aside from resistive losses in the element, the rebroadcast signal will be significantly similar to the original signal in both magnitude and shape. If this element is placed so its signal reaches the main dipole in-phase, it will reinforce the original signal, and increase the current in the dipole. Elements used in this way are known as passive elements. Question: What is a half wave dipole need to be coupled with in most instances?
feed point

Passage: Dvaita Vedanta is a dualistic interpretation of the Vedas, espouses dualism by theorizing the existence of two separate realities. The first and the only independent reality, states the Dvaita school, is that of Vishnu or Brahman. Vishnu is the supreme Self, in a manner similar to monotheistic God in other major religions. The distinguishing factor of Dvaita philosophy, as opposed to monistic Advaita Vedanta, is that God takes on a personal role and is seen as a real eternal entity that governs and controls the universe. Like Vishishtadvaita Vedanta subschool, Dvaita philosophy also embraced Vaishnavism, with the metaphysical concept of Brahman in the Vedas identified with Vishnu and the one and only Supreme Being. However, unlike Vishishtadvaita which envisions ultimate qualified nondualism, the dualism of Dvaita was permanent. Question: Of what does Dvaita Vedanta theorize the existence?
two separate realities

Passage: Uranium is a naturally occurring element that can be found in low levels within all rock, soil, and water. Uranium is the 51st element in order of abundance in the Earth's crust. Uranium is also the highest-numbered element to be found naturally in significant quantities on Earth and is almost always found combined with other elements. Along with all elements having atomic weights higher than that of iron, it is only naturally formed in supernovae. The decay of uranium, thorium, and potassium-40 in the Earth's mantle is thought to be the main source of heat that keeps the outer core liquid and drives mantle convection, which in turn drives plate tectonics. Question: Where does uranium rank among elements in terms of its abundance in the Earth's crust?

51st