Final answer:
The minimum mass required for a star to undergo a fusion reaction greater than 40 solar masses is 50 solar masses.
Step-by-step explanation:
The minimum mass required for a star to undergo a fusion reaction greater than 40 solar masses is 50 solar masses. Stars with masses greater than 50 solar masses have enough gravitational pressure and temperature in their cores to fuse hydrogen nuclei into helium through nuclear fusion. This fusion process releases a tremendous amount of energy, allowing the star to shine brightly.