At home vs. in my home

[maderay]

English Grammar Tests, Elementary Level

ESL/EFL Test #43 "Basic English Grammar", question 4

......... am an engineer.

(a) You
(b) He
(c) We
(d) I

English Grammar Tests, Elementary Level

ESL/EFL Test #43 "Basic English Grammar", answer 4

I am an engineer.

Correct answer: (d) I
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why in english there is at before the word ' home' ? why there is no ' in'?

maderay

[Mister Micawber]

.
No reason except custom. It is idiomatic.

I am at home.
I am in my home.
.
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Native English teacher at Mister Micawber's