TASK DEFINITION: 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.
PROBLEM: Passage: The Chinese intervention in late October 1950 bolstered the Korean People's Air Force (KPAF) of North Korea with the MiG-15, one of the world's most advanced jet fighters. The fast, heavily armed MiG outflew first-generation UN jets such as the F-80 (United States Air Force) and Gloster Meteors (Royal Australian Air Force), posing a real threat to B-29 Superfortress bombers even under fighter escort. Fearful of confronting the United States directly, the Soviet Union denied involvement of their personnel in anything other than an advisory role, but air combat quickly resulted in Soviet pilots dropping their code signals and speaking over the wireless in Russian. This known direct Soviet participation was a casus belli that the UN Command deliberately overlooked, lest the war for the Korean peninsula expand to include the Soviet Union, and potentially escalate into atomic warfare. Question: Who feared engaging in direct conflict with the United States?

SOLUTION: Soviet Union

PROBLEM: Passage: The word phonology comes from the Greek φωνή, phōnḗ, "voice, sound," and the suffix -logy (which is from Greek λόγος, lógos, "word, speech, subject of discussion"). Definitions of the term vary. Nikolai Trubetzkoy in Grundzüge der Phonologie (1939) defines phonology as "the study of sound pertaining to the system of language," as opposed to phonetics, which is "the study of sound pertaining to the act of speech" (the distinction between language and speech being basically Saussure's distinction between langue and parole). More recently, Lass (1998) writes that phonology refers broadly to the subdiscipline of linguistics concerned with the sounds of language, while in more narrow terms, "phonology proper is concerned with the function, behavior and organization of sounds as linguistic items." According to Clark et al. (2007), it means the systematic use of sound to encode meaning in any spoken human language, or the field of linguistics studying this use. Question: Who in 1939 defined phonology?

SOLUTION: Nikolai Trubetzkoy

PROBLEM: Passage: There are quite a few different dielectrics that can be chosen to provide different insulating values depending on the requirements of the circuit. Some of these dielectrics are polytetrafluoroethylene (Teflon), FR-4, FR-1, CEM-1 or CEM-3. Well known pre-preg materials used in the PCB industry are FR-2 (phenolic cotton paper), FR-3 (cotton paper and epoxy), FR-4 (woven glass and epoxy), FR-5 (woven glass and epoxy), FR-6 (matte glass and polyester), G-10 (woven glass and epoxy), CEM-1 (cotton paper and epoxy), CEM-2 (cotton paper and epoxy), CEM-3 (non-woven glass and epoxy), CEM-4 (woven glass and epoxy), CEM-5 (woven glass and polyester). Thermal expansion is an important consideration especially with ball grid array (BGA) and naked die technologies, and glass fiber offers the best dimensional stability. Question: To what type of packaging is thermal expansion particularly critical?

SOLUTION:
ball grid array