Brain Test Level 100 Answer
Typing kitten, which is the word the question is fishing for. Kitten is what a young cat is called, and that is exactly why it is wrong here.
The puzzle
What is a cat's child called?
The answer
Just 'cat'. A kitten is still a cat, and that is the whole trick.
What most people try first
Typing kitten, which is the word the question is fishing for.
Why that is the answer
Kitten is what a young cat is called, and that is exactly why it is wrong here. The question asks what a cat's child is, and a cat's child is a cat. The young of a species belongs to that species whatever name its age happens to carry. The level rewards you for answering the question actually asked rather than the vocabulary question it resembles.
If your level 100 looks different
Unico Studio shuffles level numbers between game versions and platforms, so the puzzle on your screen may carry a different number from the one here. If the question above is not the one you are looking at, the full levels 51 to 100 walkthrough lists every puzzle in this stretch by its question, which is easier to match than a number.