Final answer:
Citric Acid is the example of a common name among the given choices, as it is widely known by this name rather than its chemical name.
Step-by-step explanation:
The student has asked which option is an example of a common name. Among the given choices, the example of a common name is d) Citric Acid. Citric acid is widely recognized by its common name rather than its chemical name. Other options such as a) Ammonium phosphate, which is also known by its common name, have more of a connection to systematic naming, which is based on the compound's chemistry.