In the phrasal verb question, choose the option that best expresses the meaning of "turned down".

Introduction / Context:
Phrasal verbs often have idiomatic meanings that are different from the sum of their parts. The phrase turned down can be used in several contexts, but in examination English it frequently appears in the sense of rejecting an offer, request or application. We must choose the option that captures this meaning most accurately.

Given Data / Assumptions:

The target phrase is turned down.

The options are subject, object, reject, deject and reduce in volume.

The question is about general meaning, not a specific sentence.

We assume the common context of rejecting a proposal, invitation or request.

We need the closest one word substitute for the phrasal verb.

Concept / Approach:
In everyday English, to turn down an offer means to refuse or reject it politely or firmly. For example, someone can turn down a job offer or a proposal. Therefore, the single word that best replaces turned down in this sense is reject. The words subject and object are grammatical terms and do not match. Deject refers to making someone sad, and reduce in volume describes a different meaning of turn down as used with radios or televisions.

Step-by-Step Solution:
Step 1: Recall common sentences such as He turned down the offer or She turned down the invitation. In all such examples, turned down means refused or rejected. Step 2: Examine option C, reject. This is a direct and accurate one word substitute for refuse. Step 3: Examine option D, deject. Deject means to make someone unhappy or disappointed, which is different from refusing something. Step 4: Examine option E, reduce in volume. Turning down the volume is another meaning of the phrasal verb, but examination questions without context usually refer to the more common idiomatic sense of refusal. Step 5: Recognise that subject and object are unrelated grammatical terms and cannot represent the meaning of the phrasal verb.

Verification / Alternative check:
Replace turned down with reject in typical sentences: The committee turned down his proposal becomes The committee rejected his proposal, which preserves the meaning. If we used deject instead, The committee dejected his proposal is ungrammatical and would require a different structure. Reduce in volume only fits sentences about sounds or devices, not offers or requests, so it cannot be the default meaning here.

Why Other Options Are Wrong:
Subject and object are completely unrelated to the idea of refusal and do not connect with the phrasal verb at all. Deject expresses an emotional effect on a person and not the act of refusing a proposal or request. Reduce in volume describes another meaning of turn down but is not the intended sense in this phrasal verb vocabulary question.

Common Pitfalls:
Some learners may remember that turn down can refer to lowering volume and be tempted by that meaning. It is important to note that vocabulary questions usually target the more general or often examined sense, which in this case is the refusal of offers or requests. Always think of example sentences with people and offers to select the right meaning.

Final Answer:
The phrasal verb turned down most commonly means reject.