Final answer:
Te-106 undergoes alpha decay, forming Cd-102 as the product isotope.
Step-by-step explanation:
When Te-106 undergoes alpha decay, it emits an alpha particle, which is essentially a helium nucleus consisting of 2 protons and 2 neutrons. The resulting product isotope can be determined by subtracting the mass and atomic numbers of the alpha particle from the original isotope. In this case, the product isotope formed is Cd-102 (Cadmium-102).