To son, Cecil, Just a quick note before I start in earnest. When I wrote this, you were 8, still a little boy. In 2002, I was called to active duty in the Marine Corps in the war on Terrorism  . On the 11th of September 2001 when America was attacked, I knew that I would eventually  have to go and I was filled with a deep sense of sadness. That night as you and Keiko were asleep, I looked at your little faces and couldn't help but fight the tears. I knew it would be hard for you because I had a similar experience. When I was a little boy aged 6, my dad, your Grandpa Cawley, was sent to Vietnam during the war there. I remember how much I missed him, too. But now unfortunately I have come to realize just how difficult it must have been for Grandpa to be away from his children for a year. Thinking about this, I wanted to put my thoughts and feelings down for you and your sister. I am so sorry that I had to leave for such a long time. There is no place I would rather be than with you and Keiko. You two are the lights of my life. I have known no greater joy than in the few years since you two were born. I hope to have many more years with you. If this doesn't happen, then know that I love you more than words can express. If for some reason I don't make it home, I will need you to take care of your little sister and your Mom. You will be the man of the Cawley family. Be good my son and God will watch over you as he has me. I will be waiting impatiently for the time when we can all be together again. The writer of the letter may be   _  .
an American policeman an American soldier in the battle field a soldier in the Vietnam War a postman working far away from home
Question: To son, Cecil, Just a quick note before I start in earnest. When I wrote this, you were 8, still a little boy. In 2002, I was called to active duty in the Marine Corps in the war on Terrorism  . On the 11th of September 2001 when America was attacked, I knew that I would eventually  have to go and I was filled with a deep sense of sadness. That night as you and Keiko were asleep, I looked at your little faces and couldn't help but fight the tears. I knew it would be hard for you because I had a similar experience. When I was a little boy aged 6, my dad, your Grandpa Cawley, was sent to Vietnam during the war there. I remember how much I missed him, too. But now unfortunately I have come to realize just how difficult it must have been for Grandpa to be away from his children for a year. Thinking about this, I wanted to put my thoughts and feelings down for you and your sister. I am so sorry that I had to leave for such a long time. There is no place I would rather be than with you and Keiko. You two are the lights of my life. I have known no greater joy than in the few years since you two were born. I hope to have many more years with you. If this doesn't happen, then know that I love you more than words can express. If for some reason I don't make it home, I will need you to take care of your little sister and your Mom. You will be the man of the Cawley family. Be good my son and God will watch over you as he has me. I will be waiting impatiently for the time when we can all be together again. The writer of the letter may be   _  .
A. an American policeman
B. an American soldier in the battle field
C. a soldier in the Vietnam War
D. a postman working far away from home
Answer: