Final answer:
More than 600,000 Canadians served in the First World War, and this immense participation had significant societal impacts on Canada, including a shift from rural to urban living, the redefinition of gender roles, and internal conflicts such as the conscription crisis.
Step-by-step explanation:
During the First World War, Canada had a profound commitment to the war effort. Canada, being part of the British Empire at the time, entered the war automatically when Britain declared war on Germany. Approximately more than 600,000 Canadians served in the First World War, which is significantly greater than the other options provided (7000, 8 million, or about 60,000). This massive participation contributed to many societal changes and marked a period of great transition in Canadian life.
The war had a significant impact on Canadian society, leading to a shift from rural to urban living, and creating new roles for women, who were essential to the war effort on the home front and overseas. A considerable number of Canadian men serving in the war allowed for these social shifts. The legacy of the war, with the immense sacrifice of 60,000 lives lost and more affected by the consequent Halifax explosion and 1919 flu epidemic, led commentators to reflect on the notion of the 'lost generation'.
The conscription crisis of 1917 highlighted internal conflicts within Canada, particularly between English and French Canadians, further illustrating the domestic impact of the global conflict. By the end of the war, the participation and sacrifices of Canadian men were deeply felt throughout the nation and the world, marking Canada's significant contribution to the First World War.