Which one of the following events related to European integration is…

The correct answer is Option (2) → The Lisbon Treaty came into force-2012

Option (1) Unification of Germany-1990 — Correctly matched. East and West Germany were unified in October 1990.

Option (2) The Lisbon Treaty came into force-2012 — Not correctly matched. The Lisbon Treaty came into force in December 2009, not in 2012. In 2012 the EU was awarded the Nobel Peace Prize.

Option (3) Euro was introduced in 12 EU members-2002 — Correctly matched. The Euro was introduced in the 12 EU members in January 2002.

Option (4) Britain’s exit from EU-2016 — Correctly matched. In 2016 a referendum was held in Britain, and 51.9 per cent of the voters decided that Britain should exit the EU (Brexit).

Note: One can argue that Option (4) is not correctly matched either, because Britain formally left the European Union only on 31 January 2020; 2016 is the year of the referendum in which British voters decided to leave. The timeline of the chapter, however, gives 2016 as the year of Brexit, while the Lisbon Treaty year in Option (2) is wrong on any reading. Option (2) is therefore the most appropriate answer.