Instructions: In this task, you are given a context, a subject, a relation, and many options. Based on the context, from the options select the object entity that has the given relation with the subject. Answer with text (not indexes).
Input: Context: The AEK-971 is a Soviet / Russian selective fire assault rifle that was developed at the Kovrov Mechanical Plant (KMZ) by chief designer Sergey Koksharov in the late 1970s and 1980s. The primary model, the AEK-971, uses the 5.45×39mm round fed from standard 30-round or larger box magazines used by the AK-74, AK-74M, and similar weapons., The 5.45×39mm cartridge is a rimless bottlenecked rifle cartridge. It was introduced into service in 1974 by the Soviet Union for use with the new AK-74 assault rifle. It gradually supplemented, then largely replaced the 7.62×39mm round in service., Kovrov is a city in Vladimir Oblast, Russia, located on the right bank of the Klyazma River (a tributary of the Oka). Kovrov's population as of the 2010 Census was 145,214; down from 155,499 recorded in the 2002 Census, and further down from 159,942 recorded in the 1989 Census). In terms of population, it is the second-largest city in Vladimir Oblast (after Vladimir). In 1977, Kovrov's population had been estimated at 140,000., The AK-107 is a Russian 5.45×39mm assault rifle developed from the AK-100-series. It features a "balanced" operating system, similar to that used in the AEK-971. In this case, the designation AK does not indicate "Avtomat Kalashnikova" but "Alexandrov/Kalashnikov". The revised designation indicates the incorporation of a new gas system, designed by Youriy Alexandrov, for Kalashnikov-pattern rifles., The AO - 38 is a 5.45 × 39mm assault rifle and AK derivative designed by Peter Andreevich Tkachev and first to use the Balanced Automatic Recoil System ( BARS ) to improve stability giving better accuracy over AK - 74 's . Its derivatives are the AK - 107 and AEK - 971 ., Russia (from the  Rus'), also officially known as the Russian Federation, is a country in Eurasia. At , Russia is the largest country in the world by surface area, covering more than one-eighth of the Earth's inhabited land area, and the ninth most populous, with over 140 million people at the end of March 2016. The European western part of the country is much more populated and urbanised than the eastern, about 77% of the population live in European Russia. Russia's capital Moscow is one of the largest cities in the world, other major urban centers include Saint Petersburg, Novosibirsk, Yekaterinburg, Nizhny Novgorod and Samara., The AK-74 (Russian: or "Kalashnikov automatic rifle model 1974") is an assault rifle developed in the early 1970s by Russian designer Mikhail Kalashnikov as the replacement for the earlier AKM (itself a refined version of the AK-47). It uses a smaller 5.45×39mm cartridge, replacing the 7.62×39mm chambering of earlier Kalashnikov-pattern weapons., The AK-47, or AK as it is officially known (also known as the Kalashnikov) is a selective-fire (semi-automatic and automatic), gas-operated 7.62×39 mm assault rifle, developed in the Soviet Union by Mikhail Kalashnikov. It is officially known in the Soviet documentation as "Avtomat Kalashnikova"., Subject: ao-38 assault rifle, Relation: country_of_origin, Options: (A) russia (B) soviet union
Output:
soviet union