Answer:
b. root + suffix + suffix
Step-by-step explanation:
Root is the main word from which the new words with the prefixes and suffixes are made. They indicate the base of all words that can be made with the modifiers.
Suffix is the word that can be added as a modifier to the 'root' word, bringing a new word.
When we look at the word "Helpfulness", we can easily know that the word "help" is the main root from which the word "helpfulness" comes into form. "Ful" and "ness" are just added modifiers that can be added to words to make a new word. These words cannot bring forth any words as "root" words. They are just "added" words to an already meaningful word.
Thus, the right answer is Help (root) + ful (suffix) + ness (suffix).