The “black box testing” methodology enforces which kind of restriction?

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

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

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

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

Explanation:
Black-box testing is a method of software testing that examines the functionality of an application without
peering into its internal structures or workings.
https://en.wikipedia.org/wiki/Black-box_testing