instruction:
Given a scientific passage and an answer, generate a question for the given answer.
question:
Passage: Immune system organs include bone marrow, the thymus gland, the spleen, and the tonsils. Each organ has a different job in the immune system. Answer: immune system
answer:
Bone marrow, the thymus gland, the spleen, and the tonsils are organs in what body system?

question:
Passage: Sperm are produced in the testes in the process of spermatogenesis. Answer: spermatogensis
answer:
What process creates sperm?

question:
Passage: Water pollution occurs when chemicals, sewage, trash, or heat enter water resources. Water pollution is threatening the limited supply of clean, fresh water that human beings and other living things depend on. Answer: water resources
answer:
Water pollution occurs when chemicals, sewage, trash, or heat enter what?