The assertion (A) states that the impact of labour participation in the Indian nationalist upsurge in the early 1930s was weak. This is confirmed as true. Interest from labourers was significantly lacking during this period, thus the force from this group was weak in the nationalist movement. The reason (R) suggests that the ideology of the Indian National Congress was viewed as bourgeois and reactionary by the labour leaders. This is also confirmed as true. Labour leaders at that time didn`t align with the bourgeois ideas of the Congress, deeming them to be restrictive, non-progressive and potentially harmful towards the working class.

Option 1 is hence correct because both A and R are true separately, and moreover, R accurately explains why A is true. The perception of Indian National Congress`s ideology by labour leaders, plays into, and provides an explanation for the weak influence and participation of labourers in the Indian nationalist upsurge. This ties in with the historical context of labour class politics and nationalist movement in India.