In the following question, out of the four given alternatives, select the option which best expresses the meaning of the idiom or phrase “the thin end of the wedge”, that is, a small beginning that can later lead to a much larger and often harmful development.

Introduction / Context:
This question tests the meaning of a common English idiom, “the thin end of the wedge”. Idiom questions are very popular in competitive examinations because they check whether a candidate understands figurative language rather than only literal meanings. In real life communication, idioms like this are used to warn that a seemingly small action or decision may be the start of something much bigger and often harmful. Understanding this idiom helps learners interpret editorials, essays, and conversations that talk about gradual negative change in policies or social behaviour.

Given Data / Assumptions:

• The idiom provided is “the thin end of the wedge”.
• We need to select the option that best expresses its intended figurative meaning.
• Four possible meanings are given as alternative options.
• We assume standard modern British or international English usage as found in newspapers and reference dictionaries.

Concept / Approach:
The idiom “the thin end of the wedge” comes from a physical wedge used to split wood or rock. A wedge has a thin edge and a thick body. Once the thin end is inserted into a small crack and hammered in, the wider end forces the gap to become larger and larger. In language, this image is used to describe a small, apparently harmless beginning that may open the way for more serious, damaging, or undesirable developments. Therefore, the correct meaning is about the start of a harmful development, not about vigilance, tricks, or possessions.

Step-by-Step Solution:

Verification / Alternative check:
To verify, imagine a sentence from a newspaper editorial: “Allowing private companies to monitor user data may seem harmless now, but it could be the thin end of the wedge.” Here, the writer clearly warns that a small step could lead to more serious privacy violations later. If we replace “the thin end of the wedge” with “start of harmful development”, the sentence still makes complete sense. Replacing it with “in strict vigilance” or “not a worthy possession” would distort the meaning. This confirms that the idiom refers to the first small step in a future harmful process.

Why Other Options Are Wrong:

• Option A: “In strict vigilance” refers to careful watching or monitoring. The idiom does not talk about watching something, but about the beginning of a negative trend.
• Option C: “Be aware of the trick” suggests noticing a deception or trick. The idiom is not directly about a trick; it is about a small beginning that leads to larger consequences.
• Option D: “Not a worthy possession” talks about value or worth of an object. The idiom does not refer to an object or ownership, so this option is unrelated.

Common Pitfalls:
Learners sometimes misinterpret idioms word by word. They may think of “thin” as referring to physical thinness, or they may connect “wedge” with being stuck, and then guess a completely different meaning. Another common error is to pick an option that sounds vaguely negative without fully matching the idiom, such as something about tricks or unworthy possessions. In idiom questions, always recall the well known figurative meaning from usage, not from literal translation of individual words. Regular reading of quality English texts helps to fix these idioms in memory.

Final Answer:
The idiom “the thin end of the wedge” means the start of harmful development, that is, a small beginning that can lead to much bigger and more serious negative changes later.