Final answer:
The velocity of a guided wave is primarily controlled by material properties and can vary based on the waveguide geometry. The speed of a wave is determined by the medium's density and elasticity, with waveguide shape also influencing propagation velocity.
Step-by-step explanation:
The velocity of a guided wave is controlled by material properties and can also be different based on waveguide geometry. This is because the speed of a mechanical wave depends on the properties of the material such as density and elasticity (bulk modulus for fluids, Young's modulus for solids). Additionally, waveguide geometry can affect the propagation velocity, as certain shapes can dictate the boundaries and constraints through which the wave can travel. For example, the velocity of a longitudinal wave through a fluid depends on the fluid's density and bulk modulus, which are intrinsic material properties.
However, it should be noted that wave speed is typically determined by the medium's properties and not by the frequency of the wave. While the frequency can affect the wavelength, the wave speed itself remains constant for a given medium and type of wave, except for dispersion effects, which can occur in some materials and conditions.
Regarding your options, A) conventional UT (ultrasound testing) rules are general guidelines that apply to waves in a material assuming no guiding structure, B) while the speed can vary with frequency, this is typically due to dispersion rather than a fundamental property of the wave speed, and D) is a valid point as the waveguide geometry can have a considerable effect on wave speed. Therefore, the best answer reflecting the primary determinants would be that the velocity of a guided wave is 'C) controlled by material properties alone' along with an influence from 'D) different based on waveguide geometry'.