What key difference set the Kheda Satyagraha apart from the Ahmedabad Mill Strike during the phase of heightened nationalist activity?

The correct option is: Mobilisation of rural peasants versus organisation of urban workers.

To understand why this is the key difference, we can examine the distinct settings and target demographics of both movements, which took place in 1918 under the leadership of Mahatma Gandhi:

1. Kheda Satyagraha (1918):
The Kheda Satyagraha was organized in the rural Kheda district of Gujarat. The region had suffered a major crop failure, making it impossible for the local cultivators to pay the heavy land revenue taxes demanded by the colonial administration. Under the guidance of Gandhi and Sardar Vallabhbhai Patel, the campaign mobilized the rural peasantry to collectively refuse tax payments until their demands for revenue remission were met. This was fundamentally an agrarian, peasant-focused struggle against colonial land policies.

2. Ahmedabad Mill Strike (1918):
In contrast, the Ahmedabad Mill Strike occurred in the urban industrial hub of Ahmedabad, Gujarat. The dispute was not between farmers and the government, but rather between industrial cotton mill owners and the urban mill workers. The workers were demanding a 35% wage hike to offset the high cost of living and inflation during World War I, particularly after the withdrawal of the "plague bonus." Gandhi intervened by staging a hunger strike, organizing the industrial labor force to stand firm in their demands.

Summary of Difference:
Although both movements occurred around the same time and employed non-violent resistance (Satyagraha), the Kheda movement was a rural agrarian struggle involving farming communities, whereas the Ahmedabad strike was an urban labor dispute involving factory workers. Thus, the mobilization of rural peasants versus the organization of urban workers is the defining difference between the two events.