Statement: A construction worker was buried alive when mud from a 20-ft high pit collapsed on him and four others.
Assumption I: The other four people buried under the mud from the pit have been saved.
Assumption II: The 20-ft high pit collapsed owing to spurious quality of construction material used.
Because it is mentioned that one worker was buried alive we can assume that others are safe. There is nothing mentioned about the reason of this accident, hence only Assumption I is implied and correct answer is 1.