In the following question, out of the given four alternatives, select the one which best expresses the meaning of the word “Mandatory”.

Introduction / Context:
This vocabulary question tests your understanding of the word “mandatory”, which is very common in official notices, exam instructions, and legal documents. Knowing its meaning helps you understand whether a particular action is compulsory or can be skipped.

Given Data / Assumptions:

• The target word is “Mandatory”.
• Options are: Optional, Voluntary, Essential, Unnecessary.
• You must choose the synonym, i.e., the word closest in meaning.
• We assume its usual administrative or legal context: rules, requirements, etc.

Concept / Approach:
“Mandatory” means legally or officially required; compulsory; something that must be done. A close synonym needs to convey the idea of necessity or obligation, not choice. Among the given options, “Essential” means absolutely necessary and closely matches this sense of something that cannot be omitted. The other options express ideas of choice or lack of necessity, which are opposite to “mandatory”.

Step-by-Step Solution:
Recall the meaning: “mandatory” = required by rule or law; not optional.Option A – “Optional”: means something you can choose to do or skip; this is the opposite of mandatory.Option B – “Voluntary”: something done by choice, without being forced; also opposite to compulsory.Option C – “Essential”: means absolutely necessary or extremely important; very close to a mandatory requirement.Option D – “Unnecessary”: not needed; again the opposite of essential or compulsory.Therefore, “Essential” is the correct synonym for “Mandatory”.

Verification / Alternative check:
Consider an exam instruction: “It is mandatory to carry your admit card.” We can rephrase it as: “It is essential to carry your admit card.” In both cases, the idea is that you cannot be allowed in without it. Replacing “mandatory” with “optional” or “voluntary” would completely change the meaning and give the wrong impression that you have a choice.

Why Other Options Are Wrong:
“Optional” and “Voluntary” both suggest freedom of choice, which contradicts the idea of being compelled by rules. “Unnecessary” is even stronger in the opposite direction; it says something is not needed at all. None of these capture the sense of an unavoidable requirement that “mandatory” expresses, while “Essential” matches it closely.

Common Pitfalls:
Students sometimes confuse “mandatory” and “voluntary” in everyday talk, especially when reading guidelines quickly. In exam questions, always slow down and focus on the key contrast: mandatory = must do; voluntary = choose to do. If you remember that, then “Essential” becomes the obvious synonym among the options.

Final Answer:
The word that best expresses the meaning of “Mandatory” is Essential.