instruction:
Given a scientific passage and an answer, generate a question for the given answer.
question:
Passage: Figure 12.7 Statues made from carbonate compounds such as limestone and marble typically weather slowly over time due to the actions of water, and thermal expansion and contraction. However, pollutants like sulfur dioxide can accelerate weathering. As the concentration of air pollutants increases, deterioration of limestone occurs more rapidly. (credit: James P Fisher III). Answer: air pollutants
answer:
Deterioration of limestone occurs more rapidly as the concentration of what increases?

question:
Passage: Destructive interference in waves occurs when two troughs overlap. Answer: two troughs
answer:
Destructive interference in waves occurs when what things overlap?

question:
Passage: Ferns are the most common seedless vascular plants ( Figure below ). They usually have large divided leaves called fronds. In most ferns, fronds develop from a curled-up formation called a fiddlehead ( Figure below ). The fiddlehead looks like the curled decoration on the end of a stringed instrument, such as a fiddle. Leaves unroll as the fiddleheads grow and expand. Ferns grow in a variety of habitats, ranging in size from tiny aquatic species to giant tropical plants. Answer: ferns
answer:
What are the most common seedless vascular plants?