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.

[Q]: The brushless wound-rotor synchronous doubly-fed (BWRSDF) machine is the only electric machine with a truly dual ported transformer circuit topology (i.e., both ports independently excited with no short-circuited port). The dual ported transformer circuit topology is known to be unstable and requires a multiphase slip-ring-brush assembly to propagate limited power to the rotor winding set. If a precision means were available to instantaneously control torque angle and slip for synchronous operation during motoring or generating while simultaneously providing brushless power to the rotor winding set, the active current of the BWRSDF machine would be independent of the reactive impedance of the transformer circuit and bursts of torque significantly higher than the maximum operating torque and far beyond the practical capability of any other type of electric machine would be realizable. Torque bursts greater than eight times operating torque have been calculated.
[A]: What is the only device with dual ported transformer circuit topology?

[Q]: Translation is a major obstacle when comparing different cultures. Many English terms lack equivalents in other languages, while concepts and words from other languages fail to be reflected in the English language. Translation and vocabulary obstacles are not limited to the English language. Language can force individuals to identify with a label that may or may not accurately reflect their true sexual orientation. Language can also be used to signal sexual orientation to others. The meaning of words referencing categories of sexual orientation are negotiated in the mass media in relation to social organization. New words may be brought into use to describe new terms or better describe complex interpretations of sexual orientation. Other words may pick up new layers or meaning. For example, the heterosexual Spanish terms marido and mujer for "husband" and "wife", respectively, have recently been replaced in Spain by the gender-neutral terms conyuges or consortes meaning "spouses".
[A]: What tends to be a major obstacle when comparing cultures?

[Q]: Due to reciprocity (discussed above) the gain of an antenna used for transmitting must be proportional to its effective area when used for receiving. Consider an antenna with no loss, that is, one whose electrical efficiency is 100%. It can be shown that its effective area averaged over all directions must be equal to 2/4, the wavelength squared divided by 4. Gain is defined such that the average gain over all directions for an antenna with 100% electrical efficiency is equal to 1. Therefore, the effective area Aeff in terms of the gain G in a given direction is given by:
[A]:
What must the relationship of an antenna and the receiving area be due to reciprocity?