Given the Question and Answer pair, detect whether the answer is acceptable or not. Denote acceptable answer as "yes", otherwise denote as "no". An acceptable answer is consistent with the context in question, detailed, long, and uses general knowledge of English. Answers that are not definite and suggest a variety of options are not acceptable answers.

[Q]: Question: This is a question for English wordsmiths. Is there a word that "feels" like the word "ethereal" that means something ethereal that quickly disappears. Or is "ethereal" the correct word choice for this? Ethereal was the first word that popped into my head for this. From the various definitions that I've looked at for ethereal, it says delicate, beautiful, heavenly, etc. but not necessarily quickly vanishing, except for the secondary definitions related to ether that suggests it evaporates. I'm just wondering if there is a better word than this. I'm using the term "ethereal skill" to describe a certain type of pilot skill (instrument flying) that requires tremendous practice to achieve proficiency, and once proficiency is achieved it is a beautiful thing, but if you don't practice it regularly, that skill vanishes after a few weeks. USAGE: Instrument proficiency is an ethereal skill that once obtained must be maintained through constant and regular practice. 
Answer: evanescent is a good match - definitions focus on loss and vaporous qualities. It seems to be applied most often to the loss of things with positive connotation. MW defines it with : "tending to vanish like vapor", Cambridge with "lasting for only a short time, then disappearing quickly and being forgotten" Century Dictionary Online has a number of useful definitions and quotes. I like "Vanishing or apt to vanish or be dissipated, like vapor; passing away; fleeting: as, the pleasures and joys of life are evanescent. Also from Century, this quote: "He [Wordsworth] seems to have caught and fixed forever in immutable grace the most evanescent and intangible of our intuitions, the very ripple-marks on the remotest shores of being." - Lowell, Among my Books.
[A]: no


[Q]: Question: What's a word that means "not knowing everything"? This would serve as a complementary antonym of omniscient, which means having infinite knowledge, or simply "all-knowing". Thesaurus.com shows these possible words: stupid (opposite of being clever, which = being omniscient) unknowing (opposite of being knowing, which = being omniscient) fallible (opposite of being infallible, which means "not able to make mistakes", which = being omniscient, since I can know everything and still make mistakes) erring (which means "capable of making mistakes", which = being omniscient, since I can know everything and still make mistakes) imperfect (opposite of being perfect, which is a superset of being omniscient... how could I be perfect if I'm both omniscient and fallible?) faulty (which means "to have fault(s) / defect(s)", is the opposite of "to have no fault(s) / defect(s)", which means being perfect, which = being omniscient) ignorant (which means "having inadequate knowledge", is the opposite of "having adequate knowledge", which = having infinite knowledge) uneducated (opposite of being educated, which = being omniscient) unaware (opposite of being aware, which = being omniscient) uninformed (opposite of being informed, which = being omniscient) Yet, none of them are true antonyms for omniscient. Is there an alternative? 
Answer: I suggest that ignorant is the opposite.
[A]: no


[Q]: Question: Do the English have an ancient (obsolete) verb for the action of the book opening? For example, in Russian we say otkrit' (open the book), but in the Old slavonic the verb razognuti (to unbend the book) was used. 
Answer: The Middle English verb undon was often applied to opening a book (and many other objects). c1300 SLeg.Fran.(1) (LdMisc 108)159 : He on-dude e bok and e furste at he cam to at was a godspel. (He undid the book and the first that he came to - that was a gospel.) a1325 SLeg.(Corp-C 145)354/166 : Hewende him sulf for is wei & e oer vndude e bok. (He walked himself forth his way and the other undid the book.) c1475 Mankind (Folg V.a.354)797 : All e bokys in e worlde, yf ei hade be wndon, Kowde not a cownselde ws bett. (All the books in the world, if they had been undone, could not have counseled us better.) This meaning has since disappeared along with the book clasps that would have once been common on books. (To see a few examples of bindings, see "Medieval bindings" on the British Library site.).
[A]:
no