In this task, find the most appropriate number to replace the blank (indicated with _ ) and express it in words.

[EX Q]: Plazas have _ accumulations of rubbish but are covered with even layers of mud bricks and plaster.
[EX A]: no

[EX Q]: Sewage travels through _ different sets of pipes.
[EX A]: three

[EX Q]: Fruit flies have _ pairs of autosomes and one pair of sex chromosomes.
[EX A]:
three