Please answer the following question by reasoning step-by-step.
The book had deep meaning to the businessman, he always kept a copy of it beneath all his work in his what?\nOptions:\n- shoe box\n- suitcase\n- synagogue\n- briefcase\n- backpack

briefcase
Things that have deep meaning are kept in a safe place.

Briefcase is a safe place to keep things.

Book is a thing.

Briefcase is a small container.

.

Final answer: briefcase