Define crystal field splitting energy ?

(a) For the complex [Fe(CO)_(5)] write the hybridisartion , magnetc character and the spin of the complex . Define crystal fiweld splitting energy .

The complex that has highest crystal field splitting energy ( triangle ), is:

The complex that has highest crystal field splitting energy ( triangle ), is:

The complex that has highest crystal field splitting energy ( triangle ), is:

What is crystal field splitting energy ?