CRUD UX: general pattern to display legacy records that use a now-defunct combobox choice that no longer exists in combobox?

Question

Subject says it all. Is there a go-to design/UX pattern to handle this situation? I'm using Winforms ComboBoxes, but the situation is applicable to any GUI. Moreover, this is difficult to search because the search terms are very broad.

Last year, combobox options were A,B,C. Many records were saved with choice B.

This year, combobox options are A,C. But someone might want to review records from last year. Viewing those records lead to two options, both of which are undesirable.

1. Showing a blank in the combobox, making review impractical.
2. leaving the defunct item in the combobox, giving the false impression that choice B is still valid.

EDIT 1: To address the suggestions on owner drawing the ComboBox items and graying out the defunct items: I may end up going that way. But the thrust of the question was not a mechanical one, but a philosophical one. Not how to gray out items, but to question whether graying them out is the wisest option and what are some alternate approaches. Surely this is a frequently encountered snafu.