Difference between code of conduct and code of behaviour

[nancy]

Test No. incompl/advan-1 "Code of Practice", question 1

The company had its own code of ......... in these matters.

(a) behaviour
(b) practice
(c) dealing
(d) attitude

Test No. incompl/advan-1 "Code of Practice", answer 1

The company had its own code of practice in these matters.

Correct answer: (b) practice

Your answer was: incorrect
The company had its own code of behaviour in these matters.
_________________________

in question 1 why can't it be behaviour

[Torsten]

Code of behaviour is used to set the rules for students or other groups of individuals while code of conduct is the term in a business setting.

TOEFL listening lectures: A university lecture by a professor of Physics