5.試著簡述Learning Region的概念，並舉出一個實際案例加以說明。同時進一步指出該概念適合補充課程中的哪項重要概念，並說明其理由。（15分）

29. (10 points) The chromium centers in the crystal structure of KCrF₃ are in an octahedral environment of fluorine atoms. Four of the Cr-F bond distances are 214 pm, and the remaining two trans Cr-F bond distances are 201 pm. Explain these observations and include a crystal field splitting diagram.