The correct answer is career.

The sentence is about Raman's goal of joining the armed forces. The word "career" is the most appropriate word to fill in the blank because it refers to a long-term occupation or profession. Raman is preparing for a long-term career in the armed forces, so the word "career" is the best fit.

The other options are not as appropriate.

• Occupancy refers to the act of occupying a place. It is not the most appropriate word to use in this context, because Raman is not simply occupying a place in the armed forces, he is pursuing a long-term career.
• Carrier refers to a ship or aircraft that is used to transport goods or people. It is not the most appropriate word to use in this context, because Raman is not a ship or aircraft, he is a person who is pursuing a career in the armed forces.
• Postage refers to the cost of sending mail. It is not the most appropriate word to use in this context, because Raman is not sending mail, he is pursuing a career in the armed forces.