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

[EX Q]: Birds begin dying of fowl cholera _ to nine days after exposed to the virus.
[EX A]: four

[EX Q]: Pups are unable to swim or find food until seven to _ weeks old or until the ice melts .
[EX A]: eight

[EX Q]: Bivalves have _ shells, like a clam or oyster.
[EX A]:
two