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

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

[EX Q]: New species are believed to arrive in the Mediterranean at the rate of _ to five annually.
[EX A]: four

[EX Q]: Diploid organisms contain _ copies of each gene.
[EX A]:
two