In the following question, out of the four alternatives, choose the one which can be substituted as a single word for the description: "Substance used in surgery to produce unconsciousness."

Introduction / Context:
This one-word substitute question checks your knowledge of basic medical vocabulary that often appears in general English sections. The description talks about a substance used in surgery to produce unconsciousness. In real life, this is a very important concept for safe operations, and English exams expect you to know the standard technical term for such a substance.

Given Data / Assumptions:

• Description: substance used in surgery to produce unconsciousness.
• We are not talking about simple pain killers, but about controlled loss of consciousness.
• Options include Antiseptic, Antidote, Anesthetic, Cocaine, and Sedative.
• We assume general scientific and medical terminology as used in basic school texts.

Concept / Approach:
A substance that causes loss of sensation, especially pain, and that can produce unconsciousness for surgical operations is called an "anaesthetic" or "anesthetic" depending on spelling style. This word comes from Greek roots meaning "without sensation". Antiseptics kill germs on the skin, antidotes counter poisons, sedatives calm a person but do not necessarily cause full unconsciousness, and cocaine is a specific drug with limited medical uses and high abuse potential. Therefore, only "Anesthetic" correctly matches the full description.

Step-by-Step Solution:
Step 1: Focus on the key phrase "produce unconsciousness" and connect it with surgery.Step 2: Recall that before major surgery, doctors give an anesthetic so that the patient does not feel pain and becomes unconscious.Step 3: Examine the options and match them with their medical functions.Step 4: Identify "Anesthetic" as the technical term for such a substance.Step 5: Confirm that no other option describes a surgical drug that reliably produces unconsciousness.

Verification / Alternative check:
Use the word in a sentence: "The patient was given a general anesthetic before the operation." Here, the anesthetic is clearly the substance responsible for unconsciousness. If we try the same sentence with "antiseptic", it becomes "The patient was given a general antiseptic", which is wrong because antiseptics are applied to skin to prevent infection, not to make someone unconscious. Similarly, "antidote" is for poisoning, and "sedative" may relax someone but may not fully knock them out for surgery.

Why Other Options Are Wrong:

• Antiseptic: Used to kill germs and prevent infection on wounds and skin, not to cause unconsciousness.
• Antidote: A substance that counteracts a poison, quite different from surgical drugs for unconsciousness.
• Cocaine: A powerful stimulant drug that can act as a local anesthetic in some limited medical contexts, but it is not the general name for substances used in surgery.
• Sedative: A drug that calms or makes someone sleepy, but does not necessarily produce deep surgical unconsciousness.

Common Pitfalls:
Candidates sometimes confuse "sedative" with "anesthetic" because both drugs affect consciousness. The exam setter is specifically pointing to surgical operations, which require controlled deep anesthesia, not just calming. Also, the presence of a familiar but wrong medical word like "antiseptic" can mislead those who only roughly remember textbook terms. Always connect the word directly with the key idea given in the description.

Final Answer:
The correct one-word substitute for a substance used in surgery to produce unconsciousness is Anesthetic.