Final answer:
The past participle of the verb "fall" is formed by adding the suffix -en, resulting in "fallen," which is an irregular verb form.
Step-by-step explanation:
To form the past participle of the verb "fall," you would add the suffix -en, making the correct form "fallen."
This is an example of an irregular verb, where the typical -ed suffix is not used to form the past simple or past participle.
The suffix -ed does indeed add the meanings “in the past” and “action completed” to verbs and has different pronunciations like [d], [id], and [t], depending on the verb it is attached to.
However, for the verb "fall," the correct past participle is "fallen" and therefore, option b. -en is the correct answer.