Final answer:
Britain leaving the EU, known as Brexit, is historic as it signifies the first time a founding EU member state left the union, with significant implications for global politics and a major shift in European cooperation. The correct options are b,c.
Step-by-step explanation:
Britain's departure from the European Union (EU) is considered historic for several reasons, which makes option b) 'It had a significant impact on global politics' and option c) 'It marked a major shift in European cooperation' both correct answers.
Firstly, the departure, known as Brexit, represents the first instance of a founding EU member state leaving the union. The referendum held in June 2016 resulted in a narrow majority voting to leave the EU, and after several years of negotiations and political upheaval, the UK officially exited on January 31, 2020.
Secondly, Brexit has significant implications for international relations, causing concerns about trade disruption, economic consequences, and the potential for other member states to leave the EU.
Finally, Brexit reflects a shift in ideology regarding sovereignty and national identity, highlighting concerns about immigration policies and dissatisfaction with supranational governance among certain segments of the British population. The correct options are b,c.