In this task, you're given passages that contain mentions of names of people, places, or things. Some of these mentions refer to the same person, place, or thing. Your job is to write questions that evaluate one's understanding of such references. Good questions are expected to link pronouns (she, her, him, his, their, etc.) or other mentions to people, places, or things to which they may refer. Do not ask questions that can be answered correctly without understanding the paragraph or having multiple answers. Avoid questions that do not link phrases referring to the same entity. For each of your questions, the answer should be one or more phrases in the paragraph, and it should be unambiguous.
Q: Passage: The number of victims is estimated at about 22,000, with a lower limit of confirmed dead of 21,768. According to Soviet documents declassified in 1990, 21,857 Polish internees and prisoners were executed after 3 April 1940: 14,552 prisoners of war (most or all of them from the three camps) and 7,305 prisoners in western parts of the Byelorussian and Ukrainian SSRs. Of them 4,421 were from Kozelsk, 3,820 from Starobelsk, 6,311 from Ostashkov, and 7,305 from Byelorussian and Ukrainian prisons. The head of the NKVD POW department, Maj. General P. K. Soprunenko, organized "selections" of Polish officers to be massacred at Katyn and elsewhere.Those who died at Katyn included soldiers (an admiral, two generals, 24 colonels, 79 lieutenant colonels, 258 majors, 654 captains, 17 naval captains, 85 privates, 3,420 non-commissioned officers, and seven chaplains), 200 pilots, government representatives and royalty (a prince, 43 officials), and civilians (three landowners, 131 refugees, 20 university professors, 300 physicians; several hundred lawyers, engineers, and teachers; and more than 100 writers and journalists). In all, the NKVD executed almost half the Polish officer corps. Altogether, during the massacre, the NKVD executed 14 Polish generals: Leon Billewicz (ret.), Bronisław Bohatyrewicz (ret.), Xawery Czernicki (admiral), Stanisław Haller (ret.), Aleksander Kowalewski (ret.), Henryk Minkiewicz (ret.), Kazimierz Orlik-Łukoski, Konstanty Plisowski (ret.), Rudolf Prich (killed in Lviv), Franciszek Sikorski (ret.), Leonard Skierski (ret.), Piotr Skuratowicz, Mieczysław Smorawiński, and Alojzy Wir-Konas (promoted posthumously). Not all of the executed were ethnic Poles, because the Second Polish Republic was a multiethnic state, and its officer corps included Belarusians, Ukrainians, and Jews. It is estimated about 8% of the Katyn massacre victims were Polish Jews. 395 prisoners were spared from the slaughter, among them Stanisław Swianiewicz and Józef Czapski. They were taken to the Yukhnov camp or  Pavlishtchev Bor and then to Gryazovets.
A:
What percentage of victims of the massacre that included 20 university professors were estimated to be Polish Jews?