In the following error spotting sentence, identify which part contains a grammatical mistake: She was (1) quite amusing (2) at that story. (3) No error (4).

Introduction / Context:
This error spotting question focuses on the difference between adjectives that describe how someone feels and adjectives that describe the effect someone or something has on others. Words like "amused" and "amusing" are often confused by learners, and exam setters use this confusion to create questions. Your task is to determine which part of the sentence is wrong, or to confirm that the sentence has no error.

Given Data / Assumptions:

• Part (1): She was.
• Part (2): quite amusing.
• Part (3): at that story.
• Part (4): No error.
• The sentence aims to describe her reaction to a story.

Concept / Approach:
The adjective "amusing" describes something that causes amusement in others, such as "an amusing story" or "an amusing person". The adjective "amused" describes how someone feels when they find something funny. Here, the sentence structure "She was ... at that story" shows that she has a reaction to the story. Therefore, we need the feeling adjective "amused", not the effect adjective "amusing". The prepositional phrase "at that story" is acceptable, though "by that story" is also possible.

Step-by-Step Solution:
Step 1: Look at part (1): "She was". This is a normal subject plus verb link and contains no error. Step 2: Examine part (2): "quite amusing". Combined with "She was", this means she caused amusement, which is not what the following phrase suggests. Step 3: Note that part (3) says "at that story", indicating that the story is the cause and she is the one reacting. Step 4: Recognise that to describe her reaction to the story, we should use "amused" and not "amusing". Step 5: The correct sentence should read "She was quite amused at that story." Step 6: Since the only inappropriate word is in part (2), that part must contain the error.

Verification / Alternative check:
Consider both versions: "She was quite amusing at that story" and "She was quite amused at that story." The first suggests that she herself was funny while telling or reacting to the story, but the grammatical pattern "amusing at that story" is unnatural. The second clearly states that the story made her feel amused, which fits the structure with the preposition "at". Exam usage typically aims at testing the amused versus amusing distinction, so "amused" is the right correction. This confirms that part (2) is wrong.

Why Other Options Are Wrong:
Part (1) is simple and correct; "She was" is a standard opening clause. Part (3) "at that story" is acceptable because you can say "amused at that story" or "amused by that story". Part (4), "No error", cannot be chosen because we have already identified a clear adjective error. Therefore, parts (1), (3), and (4) are not the source of the grammatical problem.

Common Pitfalls:
Learners often confuse pairs like "amused/amusing", "bored/boring", and "excited/exciting". A useful rule of thumb is that adjectives ending in "ing" generally describe the cause of a feeling (for example, a boring lecture), while adjectives ending in "ed" describe the person who experiences the feeling (for example, the students were bored). Remembering this distinction will help you answer many similar questions correctly.

Final Answer:
The incorrect portion is Part (2), where "amusing" should be replaced by "amused".