In the following sentence, identify the part that contains an error, or select "No error": "You must not / look down into / parents' advice."

Introduction / Context:
This is an error spotting question that checks your understanding of phrasal verbs and correct preposition usage in English. The sentence advises that one should not disrespect or undervalue the advice given by parents. The focus is on whether the phrasal verb look down has been used with the correct preposition and object.

Given Data / Assumptions:

- Part A: You must not - Part B: look down into - Part C: parents' advice. - Part D: No error, to be selected only if all other parts are correct.

Concept / Approach:
The standard phrasal verb is look down on someone or something, which means to think that person or thing is inferior or not worth respect. The preposition required is on, not into. The phrase look down into suggests a different meaning, such as looking physically into a well or container, and does not match the intended figurative sense. Therefore, the error lies in Part B, where the incorrect preposition has been used.

Step-by-Step Solution:
Step 1: Read the complete sentence: You must not look down into parents' advice. Step 2: Recognise that the meaning intended is You must not despise or undervalue the advice given by parents. Step 3: Recall the correct phrasal verb pattern: look down on for despising or thinking badly of someone or something. Step 4: Compare this with the phrase look down into, which usually describes a physical action of directing one's gaze downward into a space. Step 5: Confirm that Parts A and C are grammatically acceptable: You must not and parents' advice both fit the context. Step 6: Conclude that the only error is in Part B, where into should be replaced with on to form look down on.

Verification / Alternative check:
Rewrite the corrected sentence: You must not look down on parents' advice. This version carries the clear sense that one should respect and value advice from parents rather than consider it inferior. The corrected preposition on fits the idiomatic pattern. No change is needed in the rest of the sentence, which confirms that Part B alone was problematic in the original version.

Why Other Options Are Wrong:
Part A, You must not, correctly introduces a negative obligation and has no grammatical error. Part C, parents' advice, is acceptable; the double apostrophe reflects that advice belongs to parents in general. Part D, No error, would be correct only if none of the segments contained mistakes, but the incorrect preposition into in Part B makes that impossible. Therefore, options A, C, and D cannot be the right answer.

Common Pitfalls:
Learners often confuse phrasal verbs with similar sounding prepositions, for example, look into, look at, and look down on. Each of these has a different meaning: look into means investigate, look at refers to directing one's eyes toward something, and look down on expresses contempt. Memorising phrasal verbs as fixed units and practising them in short example sentences helps reduce such mistakes in error spotting questions.

Final Answer:
B is the correct choice, because the phrase look down into should be look down on.