Answer:
Laertes tells her that Hamlet is only interested in her for one thing and that she should protect her maidenhead and her honor by ignoring Hamlet's attentions.
Laertes counsels his sister against unwisely allowing Hamlet to take her "honor" from her, given that he will almost certainly either change his own feelings about her or be counselled to marry someone else for political reasons.
Polonius reiterates this when he enters and asks Ophelia what she and Laertes have been talking about. He says that Ophelia is young and "green" and that it would be foolish of her to believe Hamlet's "tenders.
Explanation:
