instruction:
Given a scientific passage and an answer, generate a question for the given answer.
question:
Passage: First, notice where carbon is fixed by the enzyme Rubisco. In C-3, C-4, and CAM plants, CO 2 enters the cycle by joining with 5-carbon ribulose bisphosphate to form a 6-carbon intermediate, which splits (so quickly that it isn't even shown) into two 3-carbon 3-phosphoglycerate molecules. Now look for the points at which ATP and NADPH (made in the light reactions) add chemical energy ("Reduction" in the diagram) to the 3-carbon molecules. The resulting glyceraldehyde-3-phosphate "half-sugars" can enter several different metabolic pathways. One recreates the original 5-carbon precursor, completing the cycle. A second combines two of the 3-carbon molecules to form glucose, the universal fuel for life. The cycle begins and ends with the same 5-carbon RuBP molecule, but the process combines carbon and energy to build carbohydrates food for life. Answer: iron and magnesium
answer:
What elements do mafic minerals typically include?

question:
Passage: As erosion by groundwater continues, the ceiling of a cave may collapse. The rock and soil above it sink into the ground. This forms a sinkhole on the surface. You can see an example of a sinkhole in Figure below . Some sinkholes are big enough to swallow vehicles and buildings. Answer: sinkhole
answer:
What is formed when the ceiling of an underground cave collapses?

question:
Passage: All living cells are surrounded by a cell membrane. Plant cells (Figure 17.3 "An Idealized Plant Cell") and animal cells (Figure 17.4 "An Idealized Animal Cell") contain a cell nucleus that is also surrounded by a membrane and holds the genetic information for the cell. (For more information about genetics and DNA, see Chapter 19 "Nucleic Acids". ) Everything between the cell membrane and the nuclear membraneincluding Saylor URL: http://www. saylor. org/books. Answer: nucleus
answer:
What part of the cell is surrounded by a membrane and holds the genetic information for the cell?