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Given a scientific passage and an answer, generate a question for the given answer.

Passage: Sperm leave the epididymis through the vas deferens. As they travel through the vas deferens, they pass by the prostate and other glands. The sperm mix with secretions from these glands, forming semen. Semen travels through the urethra and leaves the body through the penis. A teaspoon of semen may contain as many as half a billion sperm!. Answer: semen
Output:
What is formed when sperm mixes with secretions from the various other glands of the reproductive system?