When conducting reference and background checks, which of the following practices is most important to adhere to in order to comply with legal standards? a. only checking references provided by the candidate and avoiding any external sources or contacts, b. focusing solely on the candidate's social media profiles to assess their personal character and suitability for the role, c. limiting the background check to only verifying educational qualifications and previous employment history, or d. obtaining written consent from the candidate before conducting any backgroud checks or contacting references