In the following question, some part of the sentence may have errors. Find out which part of the sentence has an error and select the appropriate option. If a sentence is free from error, select 'No Error'.
You must not(A)/look down into(B)/parents' advice.(C)/No error(D)

The error is in part B of the sentence.
The phrasal verb "look down into" is incorrect in this context. The intended meaning is to treat something with contempt or disregard. The correct phrasal verb to use here is "look down upon" or "look down on" (meaning to think of or treat someone/something as inferior), or alternatively "turn a deaf ear to". However, if referring to ignoring or treating advice as insignificant, "look down upon" fits structurally as a replacement for "look down into".