This level focuses on the suffixes ful and less.
The suffix ful means full of, so the word careful means full of care. The suffix less means without or lacking in, so a creature that is harmless is without harm.
Important: for root words that end with a consonant and then y, the y generally changes to an i before the suffix is added. So beauty becomes beautiful, not beautyful. But joy becomes joyful, not joiful, as there is no consonant before the y.