According to the syllabus, exploratory testing is a technique that involves simultaneous learning, test design and test execution. A tester dynamically designs and executes tests based on their knowledge, exploration of the test item and the results of previous tests. A time-boxed test session is a fixed period of time during which testing is performed. A test charter is a document that contains test objectives, scope, risks and other information to guide the testing. The answer A is correct because it describes an approach that can be used for exploratory testing. The other answers are incorrect because they describe other techniques, such as error guessing (B), compliance testing © and user acceptance testing (D).

References: Certified Tester Foundation Level Syllabus, Section 4.5.2, page 51-52.