Final answer:
In the decay mode η°→π°+π°, the particles produced are two pions.
Step-by-step explanation:
The student has asked about the decay mode of the eta-zero meson (η0). In the given decay mode, η0 decays to two pi-zero mesons (π0 + π0).
So the particles produced in this decay are two pions. This decay is a type of weak decay where the quark contents are rearranged, resulting in the production of two neutral mesons. The correct answer to this question is option (a) Two pions.