A. I'm home.
B. I'm at home.
C. I'm in home.
D. I'm in the home.
1. Which of the above are natural responses?
2. Do they all mean the same?
[Answer]
1. A and B are natural responses.
2. C is not correct. D could only be used something after it.
For example " I'm in the home of Mr John Smith" - You might here this on a TV programme where the interviewer (whatever) wants to tell you about their location.
A and B mean the same thing. A can be used to announce your arrival but B can' t. B can tell people where you are at that time - Where are you? - I'm at home. With a time reference they can be used in the same way in current speech. " I'm home this evening if you want to call me." "I'm at home this evening if you want to call me."