What is the MOST important reason why test conditions should be understandable by business stakeholders?

The most important reason why test conditions should be understandable by business stakeholders is that they should be able to review them and provide feedback to the Test Analyst, as they are the ones who know the business needs and expectations best. This way, the Test Analyst can ensure that the test conditions cover all the relevant aspects of the test basis and are aligned with the business objectives. The other reasons are not as important or not directly related to test conditions. Verified References: ISTQB® Certified Tester Advanced Level Test Analyst CTAL-TA, Section 2.2.1, page 21.