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: According to the table, aluminum has an atomic number of 13. Therefore, every aluminum atom has 13 protons in its nucleus. Iron has an atomic number of 26. Therefore, every iron atom has 26 protons in its nucleus. Carbon has an atomic number of 6. Therefore, every carbon atom has 6 protons in its nucleus. Saylor URL: http://www. saylor. org/books. Answer: nucleus
[EX A]: According to the table, aluminum has an atomic number of 13. therefore, every aluminum atom has 13 protons in its what?

[EX Q]: Passage: Occipital Bone The occipital bone is the single bone that forms the posterior skull and posterior base of the cranial cavity (Figure 7.9; see also Figure 7.8). On its outside surface, at the posterior midline, is a small protrusion called the external occipital protuberance, which serves as an attachment site for a ligament of the posterior neck. Lateral to either side of this bump is a superior nuchal line (nuchal = "nape" or "posterior neck"). The nuchal lines represent the most superior point at which muscles of the neck attach to the skull, with only the scalp covering the skull above these lines. On the base of the skull, the occipital bone contains the large opening of the foramen magnum, which allows for passage of the spinal cord as it exits the skull. On either side of the foramen magnum is an oval-shaped occipital condyle. These condyles form joints with the first cervical vertebra and thus support the skull on top of the vertebral column. Answer: occipital bone
[EX A]:
What is the single bone that forms the posterior skull and posterior base of the cranial cavity?