An old man lived in the village. He was one of the (1) ______ unfortunate people in the world. The whole village was tired (2) ______ him; he was always gloomy, he (3) ______ complained and was always in a bad mood. The (4) ______ he lived, the more vile he was becoming and the more (5) ______ were his words.

Select the most appropriate option to fill in blank number 5.

The correct option is poisonous.

Step-by-step explanation:

1. Analyze the Context:
The passage describes a gloomy, complaining, and increasingly vile old man who brings negativity to the entire village. The sentence in question is: "The more [longer] he lived, the more vile he was becoming and the more (5) ______ were his words." We need an adjective to describe the nature of his words that aligns with his vile and bitter character.

2. Evaluate the Options:
- poisonous: When used figuratively, "poisonous" describes words, remarks, or behavior that are extremely unpleasant, malicious, harmful, or filled with bitterness. In this context, it perfectly describes how his words spread misery and distress to others.
- toxic: While toxic can also mean harmful, "poisonous" is the traditional collocation used in this well-known story to describe his malicious speech.
- fatal: This means causing death or disaster. Words themselves cannot be literally fatal in this context.
- mortal: This refers to being subject to death or causing death (e.g., a mortal wound). It does not fit the context of describing someone's bitter speech.

3. Conclusion:
Therefore, poisonous is the most appropriate word to fill blank (5) as it best describes words that are malicious and spread unhappiness.