SAT OwlQuestion bank / Text Structure and Purpose
Lichens look like single organisms, but each is actually a partnership between a fungus and an alga or a bacterium. The fungus provides structure and protection, while its partner produces food through photosynthesis. More recently, scientists discovered that many lichens include a third partner, a type of yeast embedded in the lichen's outer layer. This finding suggests that the partnerships within lichens may be more complex than biologists had long assumed.
Which choice best describes the function of the third sentence in the overall structure of the text?
It explains how the fungus and its partner share food.
It provides an example of a lichen that lacks a fungus.
It questions whether lichens actually perform photosynthesis.
It reports a discovery that complicates the description of lichens given earlier in the text.
Show answer and explanation
Answer: D
The first two sentences describe lichens as two-member partnerships. The third reports that many lichens have a third partner, and the last sentence says this makes lichens more complex than assumed. So the third sentence introduces a complicating discovery, choice D.
Choice B misreads the discovery; the yeast is an added partner, and the fungus is still present.
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