TASK DEFINITION: In this task, find the most appropriate number to replace the blank (indicated with _ ) and express it in words.
PROBLEM: Yews typically have _ flushes of growth each growing season.

SOLUTION: two

PROBLEM: Gravity is the weakest of all _ forces but unlike the others it has an unlimited range.

SOLUTION: four

PROBLEM: Ants comprise _ main castes, which have different roles, workers, queens and males.

SOLUTION:
three