Detailed Instructions: In this task, you're given a question, a context passage, and four options which are terms from the passage. After reading a passage, you will get a brief understanding of the terms. Your job is to determine by searching and reading further information of which term you can answer the question. Indicate your choice as 'a', 'b', 'c', or 'd'. If you think more than one option is plausible, choose the more probable option to help you answer the question.
Problem:Question: Leaders of which countries signed a joint declaration on 12 May 1990? Passage:On 12 May 1990 the leaders of the Baltic republics signed a joint declaration known as the Baltic Entente. By mid-June the Soviets started negotiations with the Baltic republics on condition they agreed to freeze their declarations of independence. The Soviets had a bigger challenge elsewhere, in the form of the Russian Federal Republic proclaiming sovereignty in June. Simultaneously the Baltic republics also started to negotiate directly with the Russian Federal Republic. In Autumn 1990, they set up a customs border between the Baltic states, the Russian Federation and Belarus. After the failed negotiations the Soviets made a dramatic attempt to break the deadlock and sent troops to Lithuania and Latvia in January 1991. The attempts failed, dozens of civilians were killed, and the Soviet troops decided to retreat. In August 1991, the hard-line members of the Soviet government attempted to take control of the Soviet Union. One day after the coup on 21 August, the Estonians proclaimed independence. Shortly afterwards Soviet paratroops seized the Tallinn television tower. The Latvian parliament made similar a declaration at the same day. The coup failed but the Collapse of the Soviet Union became unavoidable. On 28 August, the European Community welcomed the restoration of the sovereignty and independence of the Baltic states. The Soviet Union recognised the Baltic independence on 6 September 1991. The Russian troops stayed for an additional three years, as Boris Yeltsin linked the issue of Russian minorities with troop withdrawals. Lithuania was the first to have the Russian troops withdrawn from its territory in August 1993. On 26 July 1994 Russian troops withdrew from Estonia and on 31 August 1994, Russian troops withdrew from Latvia. The Russian Federation ended its military presence in Estonia after it relinquished control of the nuclear facilities in Paldiski on 26 September 1995 and in Latvia after Skrunda-1 suspended operations on 31 August 1998 and subsequently dismantled. The last Russian soldier left Skrunda-1 in October 1999, thus marking a symbolic end to the Russian military presence on the soil of the Baltic countries.
 Links: a. European Communities b. Skrunda-1 c. Baltic Entente d. The Barricades
Solution:
c