What does "up to his ears in" mean?

[Minio]

English Idioms and Expressions, Intermediate level

ESL/EFL Test #1 "Up to his ears", question 1

He's up to his ears in work and cannot possibly see you now.

(a) fully occupied with
(b) very interested in
(c) not involved with
(d) concerned with

English Idioms and Expressions, Intermediate level

ESL/EFL Test #1 "Up to his ears", answer 1

He's fully occupied with work and cannot possibly see you now.

Correct answer: (a) fully occupied with
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Hi, Could you explain me what does "up to his ears in" mean?

Thank you
Minio

[Alan]

Hi,

This suggests in the sentence that he has so many things to do/he is so busy that he cannot stop and see you now.

It gives the idea that the work is piled up so high that it almost reaches his ears.

Alan
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English as a Second Language
You can read my ESL story Word Story: Jokes

[Conchita]

The idiom 'up to your ears (in something)' is normally used to suggest that you have too much work.