instruction:
This task is about reading the given passage and construct a question about the information present in the passage. Construct a question in such a way that (i) it is unambiguous, (ii) it is answerable from the passage, (iii) its answer is unique (iv) its answer is a continuous text span from the paragraph. Avoid creating questions that (i) can be answered correctly without actually understanding the paragraph and (ii) uses same words or phrases given in the passage.
question:
However a log-periodic dipole array consists of a number of dipole elements of different lengths in order to obtain a somewhat directional antenna having an extremely wide bandwidth: these are frequently used for television reception in fringe areas. The dipole antennas composing it are all considered "active elements" since they are all electrically connected together (and to the transmission line). On the other hand, a superficially similar dipole array, the Yagi-Uda Antenna (or simply "Yagi"), has only one dipole element with an electrical connection; the other so-called parasitic elements interact with the electromagnetic field in order to realize a fairly directional antenna but one which is limited to a rather narrow bandwidth. The Yagi antenna has similar looking parasitic dipole elements but which act differently due to their somewhat different lengths. There may be a number of so-called "directors" in front of the active element in the direction of propagation, and usually a single (but possibly more) "reflector" on the opposite side of the active element.
answer:
What type of antenna formation is made up of multiple dipole elements of varying lengths?


question:
Conversely, some Slavs were assimilated into other populations. Although the majority continued south, attracted by the riches of the territory which would become Bulgaria, a few remained in the Carpathian basin and were ultimately assimilated into the Magyar or Romanian population. There is a large number of river names and other placenames of Slavic origin in Romania.[better source needed]
answer:
Slavs that remained in the Carpathian basin were assimilated into who?


question:
The Chronicle provides a mythic tale of Oleg's death. A sorcerer prophesies that the death of the Grand Prince would be associated with a certain horse. Oleg has the horse sequestered, and it later dies. Oleg goes to visit the horse and stands over the carcass, gloating that he had outlived the threat, when a snake strikes him from among the bones, and he soon becomes ill and dies. The Chronicle reports that Prince Igor succeeded Oleg in 913, and after some brief conflicts with the Drevlians and the Pechenegs, a period of peace ensued for over twenty years.
answer:
What known document tells of the death of Oleg?