Select the synonym (word closest in meaning) of "rot".

Introduction / Context:
This vocabulary question asks you to select the synonym of the verb or noun "rot". Knowing a range of words for similar concepts helps you understand descriptive passages, science texts, and everyday language where processes of spoiling and decomposition are discussed.

Given Data / Assumptions:

• Target word: "rot".
• Options: mature, stagnate, smell, decay.
• You must choose the word with the closest meaning to "rot".

Concept / Approach:
"Rot" refers to the process of decomposing or spoiling, especially organic matter such as fruit, wood, or flesh. It can be used both as a noun ("the rot") and as a verb ("to rot"). Therefore, the correct synonym should point to a similar process of decomposition or deterioration, not just any negative process.

Step-by-Step Solution:
Step 1: Recall that "rot" suggests breaking down of material due to bacteria, fungi, or time, leading to spoilage. Step 2: Examine "mature". This means to become fully developed or ripe. It is often a positive process, especially with fruits and people. Step 3: Examine "stagnate". This means to stop flowing or developing, for example, water that stops moving or a career that does not progress. It does not specifically mean to decay physically. Step 4: Examine "smell". While things that rot often smell bad, "smell" describes the sensation or odour itself, not the process of decaying. Step 5: Examine "decay". "Decay" means to gradually decompose or break down, which matches the meaning of "rot" closely. Step 6: Conclude that "decay" is the best synonym.

Verification / Alternative check:
Consider example sentences: "The fruit began to rot in the basket." → "The fruit began to decay in the basket." The substitution works naturally and keeps the meaning. However, substituting other options yields unnatural sentences such as "began to mature" or "began to stagnate", which change the meaning. This confirms that "decay" is the closest synonym.

Why Other Options Are Wrong:
"Mature" refers to growth towards full development or ripeness, often before any rot or decay sets in. "Stagnate" is about stillness and lack of progress rather than physical decomposition. "Smell" describes the sensation of odour, which may be a result of rot, but it is not the same as the process of rotting.

Common Pitfalls:
A common trap is to pick a word associated with negative situations, such as "stagnate", without checking whether it refers to physical decomposition. Exam setters may include words from the same general context, but only one will match the precise meaning. Learning words in groups, such as rot, decay, decompose, and spoil, helps you recognise true synonyms quickly and avoid confusion.

Final Answer:
The synonym of "rot" is "decay".