In the following idiom based question, select the option that best expresses the meaning of the phrase "a thorn in the flesh".

Introduction / Context:
This question examines your understanding of another common English idiom, "a thorn in the flesh". Idioms often have historical or literary origins and their meanings are not obvious from the individual words. In modern usage, this phrase is commonly found in political commentary, workplace discussions and everyday conversation, and it has a fairly stable figurative meaning. Your task is to choose the explanation that best matches that established meaning.

Given Data / Assumptions:

• The idiom given is "a thorn in the flesh".
• The options suggest various possible interpretations, involving discomfort, fighting, trouble and relationships.
• The phrase clearly has a negative connotation, since a thorn in the flesh would be painful.
• We assume contemporary usage in general English, not a rare or technical sense.

Concept / Approach:
Literally, a thorn stuck in your flesh would cause constant pain and irritation until it is removed. Figuratively, "a thorn in the flesh" or "a thorn in the side" refers to a person, problem or situation that keeps causing difficulty or annoyance over a long period. It may not be life threatening, but it is persistent and troublesome. The correct option therefore must capture this idea of continuous irritation or trouble, rather than a brief or small discomfort. It should also not narrow the meaning too much, for example by limiting it only to family members.

Step-by-Step Solution:
Step 1: Recall the figurative meaning: something or someone that causes sustained trouble or irritation. Step 2: Read each option and see which one mentions continual annoyance or trouble rather than a single event or a minor issue. Step 3: Notice that the option "A source of continual annoyance or trouble" matches the remembered meaning very closely. Step 4: Confirm that the other options either describe a different situation altogether or are too narrow to represent the idiom correctly.

Verification / Alternative check:
Imagine contexts like these: "The opposition party has been a thorn in the flesh of the government" or "That constant noise from the street is a thorn in my flesh". In both cases, the phrase describes a continuing problem. If we replace it with "a source of continual annoyance or trouble", the sentences retain the same sense. In contrast, if we try "a minor discomfort which is easily ignored", the effect is reduced, because the idiom usually suggests something more persistent and harder to ignore. This kind of mental substitution confirms that the chosen explanation aligns with real usage.

Why Other Options Are Wrong:
"A minor discomfort which is easily ignored" understates the sense of the idiom. A thorn embedded in flesh is painful and difficult to ignore, so this option is misleading. "To fight despite being injured" describes courage or endurance, not ongoing irritation caused by something. "A person within close family whom you secretly hate" is too specific; while a family member could indeed be a thorn in the flesh, the idiom is not limited to family contexts. "A small injury that heals quickly" again treats the problem as short term, whereas the idiom emphasises persistence. Therefore, only the option that mentions continual annoyance or trouble is acceptable.

Common Pitfalls:
Some learners over interpret idioms emotionally and choose options that exaggerate hatred or extreme conflict. Others treat the words literally and focus only on physical injury. The best approach is to recall where you have seen the idiom used in articles or books. Typically, it refers to political opponents, irritating regulations, noise, or difficult people at work, all of which are ongoing sources of trouble. Remembering such usage patterns will guide you to the correct answer even if the literal image seems confusing at first.

Final Answer:
"A thorn in the flesh" means a source of continual annoyance or trouble.