Here are some synonyms for "duty or task to be fulfilled":
* Responsibility
* Obligation
* Chore
* Assignment
* Mission
* Mandate
* Charge
* Role
Here are some examples of how "duty or task to be fulfilled" can be used in a sentence:
* "It is the duty of every citizen to pay their taxes."
* "Her task was to prepare the presentation for the meeting."
* "He felt a strong obligation to help his family."
* "The company has a mandate to provide excellent customer service."
The specific meaning of "duty or task to be fulfilled" will depend on the context in which it is used.