Step 1: Understanding composition of semen.
Semen consists of secretions from testes and accessory glands such as seminal vesicles, prostate, and Cowper’s gland.
Step 2: Source of fructose.
Seminal vesicles secrete fructose which provides energy for sperm motility.
Step 3: Conclusion.
Hence, fructose is contributed to semen by seminal vesicles.