TASK DEFINITION: Given a sentence, fill out the missing word with a 'no' or a number (between zero and ten). You should write the numbers with english alphabet, like: four instead of 4.
PROBLEM: Sponges have ____ main tissue layers.

SOLUTION: three

PROBLEM: Sponges are subdivided into ____ classes.

SOLUTION: three

PROBLEM: Aboriginal society is divided into ____ complementary branches.

SOLUTION:
two