You are implementing an ASP.NET application. You add the following code segment. You need to add code to return a list of all Person objects except those with a UserId that is contained in the secretUsers list. The resulting list must not contain duplicates. Which code segment should you use？（）

• A、var secretPeople = （from p in allPeople from u in secretUsers  where p.UserId == u select p）.Distinct（）； return allPeople.Except（secretPeople）；
• B、return from p in allPeople from u in secretUsers where p.UserId != u select p；
• C、return （from p in allPeople  from u in secretUsers where p.UserId != u select p）.Distinct（）；
• D、List people = new List（ from p in allPeople from u in secretUsers where p.UserId != u select p）； return people.Distinct（）；