Mixed questions do not announce which relative-clause rule you need. Your job is to diagnose the clause from its meaning and internal gap before choosing a form.
Use a short decision path
Begin with punctuation and meaning. A defining clause identifies which person or thing is meant and has no commas; a non-defining clause adds information about an already identified referent and uses commas. That is unavailable in a non-defining clause, and its relative marker cannot be omitted. Then rebuild the smaller statement inside the clause and locate the gap.
| Gap or signal | Method and tiny example |
|---|---|
| The antecedent performs the action | Use a subject relative form and keep it: the baker who called. |
| The antecedent receives the action | Use an object relative form; in a defining clause it may be omitted: the bread we ordered. |
| A following noun belongs to the antecedent | Use whose for a person or thing: a lamp whose shade cracked. |
| A preposition expresses the relationship | Keep it stranded or front it before which or whom: the pier at which boats stop. |
| The gap means place, time or reason | Use the matching relative adverb only when the clause needs that relationship: the season when swallows return. |
| A quantity describes members of an earlier set | Use quantity plus of whom for people or of which for things: ten guests, three of whom stayed. |
| The relative clause contains a verb that changes for number | Trace the relative form back to its antecedent: the files that remain. |
Finish with two checks. Make sure the relative form itself fills the intended role, so you have not repeated the antecedent with another pronoun. Then confirm that the clause is complete and that its finite verb agrees with the noun phrase the relative form represents.
Wrong turns in mixed questions
- The relative form is chosen only because the antecedent names a person, thing or place. That first classification helps, but the gap may instead require possession, a direct object or an adverbial relationship.
- A relative marker is omitted whenever the clause is defining. Omission is limited to an object gap; a subject gap still needs a visible relative form.
- That is placed after a comma or used to comment on a whole preceding event. Non-defining information requires a wh-form, and which can refer to the preceding situation as a whole.
- A second personal or object pronoun is added inside the clause. The relative form already replaces the antecedent in its grammatical role, so the repeated referent makes the clause nonstandard.
- Agreement follows the nearby plural group even when the meaning identifies one unique member. Trace the relative form to the intended antecedent before choosing the finite verb.
Try it
Complete by omitting the object relative pronoun as requested: The candidate ___ sent a thank-you note. I interviewed the candidate yesterday.
Write exactly six words: begin with for which, then use the grant as the subject and the simple-past be-passive of create. The community project ___ opened its first workshop today.
Complete with that followed by we as the subject and the simple past of review. The proposal ___ received unanimous support.