Read the following passage and answer the item that follows. Your answer to this item should be based on the passage only.

Disease burden in a community is shaped by conditions operating at several nested levels: what happens inside a single household, what happens across a neighbourhood's shared water and waste systems, and what happens at the level of the wider public-health system. Improving hygiene at the household level reduces disease meaningfully, but experience elsewhere shows that household-level improvement alone plateaus quickly unless it is matched by neighbourhood-level investment in clean water, sanitation and waste management, since infection can still spread through these shared channels regardless of any one household's own practices.

On the basis of the passage given above, the following assumptions have been made:

1. Households that maintain excellent hygiene are entirely unaffected by neighbourhood-level sanitation failures.

2. Individual household effort has diminishing returns without matching community-level infrastructure.

3. Investment purely in household-level hygiene campaigns is unlikely to fully control community disease burden.

Which of the above assumptions are valid?