Choose the correct option to fill in the blank in the following sentence.
A good ________ who is able to get the best from those placed under his charge.

The correct answer is Option D (Disciplinarian).

Key Points:
• Concept: Correct English Spellings.
• Explanation: The correct spelling for a person who believes in or enforces strict discipline is D-I-S-C-I-P-L-I-N-A-R-I-A-N ('Disciplinarian').
• Other Options: All other options contain incorrect spelling arrangements ('Disciplenarian', 'Disciplinearin', 'Disiplinarian').
• Official Key: Option 4 ('Disciplinarian') is the official correct answer.
• Key Takeaway: Remember: The correct spelling is 'Disciplinarian' (d-i-s-c-i-p-l-i-n-a-r-i-a-n).