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

[EX Q]: Passage: The bodies of organisms can make a sedimentary rock. Plant bodies are lithified to become coal. When shells are cemented together they make a type of limestone. So limestone can be considered chemical or organic. Answer: coal
[EX A]: What is formed when plant bodies are lithified?

[EX Q]: Passage: In sexually reproducing organisms, parents pass a copy of each type of chromosome to their offspring by producing gametes. When gametes are fertilized and form offspring, each has a unique combination of chromosomes and genes from both parents. The inherited gene combination determines the characteristics of the offspring. Answer: chromosome
[EX A]: In sexually reproducing organisms, parents pass a copy of each type of what to their offspring by producing gametes?

[EX Q]: Passage: Oxygen chemically weathers rock by combining with a metal. Answer: oxygen
[EX A]:
What element chemically weathers rock by combining with a metal?