Final answer:
The collimator is not part of the CT tube.
Step-by-step explanation:
The answer is 2) collimator. A CT (computed tomography) tube consists of several components, including the tungsten target, rotating anode, and filament. The tungsten target is the part of the tube where the high-energy electrons from the filament collide, producing x-rays. The rotating anode helps to dissipate the heat generated during the x-ray production process. The filament is responsible for emitting the electrons that collide with the target.