Step 1: Understanding the Concept:
We need a synonym for "tetchy" as used in "why he has so tetchy with his wife", describing how the man behaved toward his wife.
Step 2: Key Formula or Approach:
To find the closest synonym, replace the underlined word with each option in the sentence and check which one keeps the same meaning and tone.
Step 3: Detailed Explanation:
"He asked his friend why he has so jealous with his wife" suggests envy, which is not what the sentence describes; the man is not shown wanting something his wife has.
"He asked his friend why he has so unfriendly with his wife" suggests coldness, which is close but misses the short-fused, snapping quality tied to "tetchy".
"He asked his friend why he has so irritable with his wife" fits naturally, since "tetchy" specifically describes someone quick to get annoyed or short-tempered over small things.
"He asked his friend why he has so conceited with his wife" points to excessive self-pride, a completely different trait from being short-tempered.
Replacing the word confirms that "irritable" preserves the original meaning most closely.
Step 4: Final Answer:
"Tetchy" means irritable or bad-tempered, so option (c) is correct.