In this English grammar error-spotting question on idiomatic expressions, identify which part of the sentence is incorrect: "My heart (A) is so full (B) for words. (C) No Error. (D)". Choose the option that marks the erroneous segment or select 'No Error' if the sentence is fully correct.

Introduction / Context:
This question focuses on the correct idiomatic expression used to describe an overwhelming emotional state. The sentence tries to convey that the speaker's heart is overflowing with emotion to such an extent that words fail. To answer correctly, you must recognise the standard idiom and identify which part of the sentence deviates from it in terms of word choice and degree adverb usage.

Given Data / Assumptions:

• Sentence: "My heart is so full for words."
• Part A: "My heart"
• Part B: "is so full"
• Part C: "for words."
• Part D: indicates "No Error".
• The intended idiom in English is "too full for words".

Concept / Approach:
In English, the standard idiomatic expression is "too full for words", meaning "so overwhelmed with emotion that one cannot find words to express it". The structure "too + adjective + for words" expresses excess beyond what is manageable. The use of "so" instead of "too" in this context breaks the idiom. While "so full" can be used in other contexts ("so full of joy", "so full of people"), the phrase "so full for words" is not idiomatic. The prepositional phrase "for words" is correct when combined with "too full", not "so full". Hence, the error lies in Part B rather than Part C.

Step-by-Step Solution:
Step 1: Check Part A: "My heart". This is a correct and natural subject phrase referring to the speaker's emotional centre. Step 2: Examine Part B: "is so full". Grammatically, "is so full" is possible, but within the expression "so full for words", it does not match any recognised idiom. Step 3: Examine Part C: "for words." In the idiom "too full for words", this prepositional phrase occurs correctly and expresses the idea that words are inadequate. Step 4: Therefore, the correct idiomatic sentence should be: "My heart is too full for words." Step 5: Since only the use of "so" in Part B violates the established idiom, Part B is the erroneous segment.

Verification / Alternative check:
Compare the two versions: "My heart is so full for words" versus "My heart is too full for words." The second version is commonly found in literature and speech and clearly expresses overwhelming emotion. The first version sounds odd because "so full for words" is not a standard combination in English. You could say "My heart is so full of emotion" or "My heart is too full for words", but mixing "so full" with "for words" is not acceptable in exam level grammar.

Why Other Options Are Wrong:

• Part A: Correctly introduces the subject and contains no grammatical error.
• Part C: The phrase "for words" is the correct second half of the idiom "too full for words". It is Part B that needs adjustment, not Part C.
• Part D (No Error): Cannot be chosen because the idiom is clearly misused with "so" instead of "too".
• Error in more than one part: Not valid; only the degree adverb in Part B must be changed.

Common Pitfalls:
Students often confuse degree adverbs "so" and "too" because both indicate a high degree. However, "too" usually implies an excessive degree that causes a problem or limitation ("too hot to go out", "too tired to study"). Idioms like "too full for words" follow this pattern. Misusing "so" in place of "too" can distort or weaken the intended meaning. Learning common idioms as fixed expressions helps avoid such mistakes in error-spotting questions.

Final Answer:
The incorrect segment is Part B: "is so full"; the correct idiomatic sentence is "My heart is too full for words.".