Final answer:
The test of reactive agility that starts with an initial straight-line run and then a 45 degree cut in response to a stimuli is called the T-Test.
Step-by-step explanation:
The test of reactive agility that starts with an initial straight-line run and then a 45 degree cut in response to a stimuli is called the T-Test. In the T-Test, the athlete runs forward in a straight line and then upon a stimulus, cuts to the left or right at a 45 degree angle. This test measures an athlete's ability to react quickly and change direction.