Selecting the right test technique is crucial because different techniques are suited to different types of testing and can significantly increase the effectiveness of the testing process by creating tests that are more likely to find defects. While reducing the number of tests (A) and defining the number of regression cycles (D) are considerations in the testing process, they are not the primary reasons for selecting a test technique. The assertion that the only way to test a software application is by using well-proven test techniques (B) is too restrictive and does not acknowledge the adaptability required in testing to suit different contexts and objectives. Therefore, option C is the most comprehensive reason, as it focuses on the effectiveness and efficiency of testing, leading to the creation of high-quality tests that have a higher chance of finding bugs.