A wh-question is used for seeking content information relating to persons, things, facts, time, place, reason, manner, etc. Wh-questions differ depending on the kind of content information sought. Content information associated with persons, things, and facts is generally sought with one set of wh-words, and content information associated with time, place, reason, and manner is sought with another set of wh-words.
Persons, things, facts: who, what, whose, which
Time, place, reason, and manner: when, where, why, how
Questioning Subject and Object Positions
With respect to sentence structure, content information associated with persons, things, and facts occurs in various subject and object positions within a sentence. Consider the question below and its possible answer.
Q: Who manages your company’s payroll system.
A: A local payroll firm manages our company’s payroll system.
This question with who refers to the content information in the highlighted subject position of the answer. In this case, the subject is the noun phrase, a local payroll firm.
In the next set, what refers to the content information in the highlighted object (or "complement") position in the answer after the verb said. In this case, the object is an entire clause, that a good accounting system is vital to a company’s success.
Q: What did the accountant say?
A: The accountant said that a good accounting system is vital to a company’s success.
In the next set, which marketing plan refers to the highlighted object of preposition position after the preposition about in the answer. In this case, the object of the preposition is a complex noun phrase, the marketing plan that was recently implemented.
Q: Which marketing plan were you talking about?
A: They were talking about the marketing plan that was recently implemented.
These examples illustrate that the information associated with persons, things, and facts is generally represented in sentence structure by noun phrases and clauses in various subject and object positions. In linguistic theory, these are known as "argument positions."
Questioning Other Sentence Positions
With respect to sentence structure, content information associated with time, place, reason, and manner does NOT occur in subject and object positions within a sentence. Consider the question below and its possible answer.
Q: When does your company begin its fiscal year?
A: My company begins its fiscal year on July 1.
This question with when refers to the content information in the highlighted portion of the answer. The phrase on July 1 pertains to time and is not a subject or an object.
In the next set, the question with why refers to the content information highlighted in the answer in the clause beginning with because. The clause, which expresses a reason, is not a subject or an object of the main clause, The accountant debited the account.
Q: Why did the accountant debit that customer’s account?
A: The accountant debited the account because the customer’s check bounced.
In linguistic theory, these positions associated with time, place, reason, and manner are known as "adjunct positions."
There is a fundamental difference between argument and adjunct positions. Argument positions (subjects, objects) are required in a sentence structure; adjunct positions are optional. This difference can be seen if the targeted arguments and adjuncts are removed from the answers to the above questions:
ARGUMENTS:
*… oversees our company’s payroll system
*The accountant said …
ADJUNCTS:
My company begins its fiscal year …
The accountant debited the account …
The * means that the sentences with missing arguments are ungrammatical. The sentences with missing adjuncts contain less information, but they are nevertheless well-formed, grammatical sentences. This difference has a bearing on wh-question formation.