In the following English idiom question, the phrase "Out of sorts" is used. From the four given alternatives, choose the option that best expresses the idiomatic meaning of this phrase as it is commonly used in everyday English.

Introduction / Context:
The idiom "out of sorts" is a common expression in English that describes someone who is not feeling well, either physically or emotionally. It is frequently used in casual speech and literature, and exam questions often test whether candidates can recognise this mild but important description of health or mood. Understanding such idioms helps learners interpret conversations and texts more accurately.

Given Data / Assumptions:
- The idiom given is "Out of sorts".
- The options are: to be equal to, to be unwell, to make peace, and to ignore.
- Only one option correctly represents the meaning of the expression in standard English.
- We assume contexts where someone is being asked about their health or state of mind.

Concept / Approach:
"Out of sorts" usually implies that a person is feeling slightly ill, tired, irritable, or not their usual cheerful self. It does not normally mean serious illness, but rather a general sense of not being in good form. Therefore, our task is to choose an option that recognises this sense of mild unwellness, instead of unrelated notions such as equality, peace making, or ignoring someone.

Step-by-Step Solution:
Step 1: Recall common usage examples like "She has been out of sorts all day" or "He seems a bit out of sorts after the long journey". Step 2: Interpret these sentences. In both cases, the speakers mean that the person is not feeling well or is somewhat upset or off balance. Step 3: Examine option B, "To be unwell". This directly corresponds to the idea of not feeling fine, physically or emotionally. Step 4: Evaluate option A, "To be equal to". This has no relation to mood or health; it is about equivalence and is clearly unrelated. Step 5: Evaluate option C, "To make peace". This describes resolving conflict, which does not fit the context of personal physical or emotional condition. Step 6: Evaluate option D, "To ignore". This is about paying no attention to someone or something and again has nothing to do with feeling unwell. Step 7: Hence, option B must be the correct answer.

Verification / Alternative check:
Standard dictionary entries for "out of sorts" define it as "slightly unwell or upset". If we replace "out of sorts" with "unwell" in example sentences, the sense remains intact: "She has been unwell all day" also explains why her mood or behaviour is different. None of the other options can substitute into those sentences without making them strange or meaningless. This confirms that the idiom refers to a minor health or mood problem rather than any other concept.

Why Other Options Are Wrong:
- "To be equal to" deals with equivalence in value or capability and does not describe a person's condition or feelings.
- "To make peace" is about ending a disagreement or conflict, not about how someone feels physically or mentally.
- "To ignore" is an action that someone chooses to take toward others or situations, not a description of their health or mood.

Common Pitfalls:
Because the words "out of" can appear in many phrases, some learners may confuse "out of sorts" with expressions like "out of order" or "out of stock". Another mistake is to interpret "sorts" in a literal way and think about types rather than emotional state. The safest method is to remember this idiom as a fixed, ready made phrase used when someone is not quite themselves, possibly a little sick, tired, or bad tempered.

Final Answer:
The idiom "Out of sorts" means to be unwell or not in one's usual good health or mood.