Answer: a. Gather all the information
d. Be patient with the reaction
Step-by-step explanation:
It is very important that before the conversation begins, that you have all the relevant information you will need to find out why they are so hostile to the new employee to avoid judging them prematurely and therefore putting them on the defensive which will not do well for the progress of the conversation. It will also help you detect any lies that they may have.
When the conversation is also going on along, let them explain themselves and be very patient with them as they do so. This way you will listen to respond not listen to react. This way you can hear their side of the story before making an informed decision.