The “white box testing” methodology enforces what kind of restriction?

A.
The internal operation of a system is completely known to the tester.

B.
Only the external operation of a system is accessible to the tester.

C.
Only the internal operation of a system is known to the tester.

D.
The internal operation of a system is only partly accessible to the tester.

Explanation:
White-box testing (also known as clear box testing, glass box testing, transparent box testing, and structural
testing) is a method of testing software that tests internal structures or workings of an application, as opposed
to its functionality (i.e. black-box testing). In white-box testing an internal perspective of the system, as well as
programming skills, are used to design test cases.
https://en.wikipedia.org/wiki/White-box_testing