Answer:
O point out important information to the reader
Step-by-step explanation:
Key phrases are phrases that enhance important information for the reader, in relation to a text. This is because these phrases show the most relevant information that should not be left out, as they act as the "key" to unlock reasoning and reflection on the subject to which the text refers.
These sentences are very useful when a summary must be done, because they are the ones that present the information that the summary should contain.