$13.$Even after leaving office, legal counsel and advisors to President Trump claimed "executive privilege" to avoid questions of a House committee investigating the January $6,2021,$ riot at the U$.$S$.$ Capitol. What is this privilege, presuming $($arguably or not$)$ that it exists in this case?

a$.$ the right of presidents to keep discussions with counsel and advisors confidential

b$.$ the ability of presidents and White House staff to maintain secrecy about absolutely anything

c$.$ the waiving of prosecution for any crimes that White House staff may commit in carrying out their constitutional duties

d$.$ a judicially created rule granting confidentiality to presidents and advisors on matters involving national security or the details of election campaigns