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Question

Difficulty: EasyRecognizing Explicit Cause and Effect

Passage:

The Black Sea possesses a unique hydrological structure that makes it one of the world's most exceptional underwater archaeological sites. Unlike most seas, the Black Sea receives massive amounts of fresh water from major European rivers, which floats above the denser, saltier water entering from the Mediterranean Sea. Because these two water layers do not readily mix, atmospheric oxygen is unable to penetrate below a depth of approximately 150 meters. This creates a vast anoxic zone—an environment entirely depleted of dissolved oxygen—that extends down to the seafloor.

Because wood-boring organisms such as Teredo navalis (commonly known as shipworms) require oxygen to survive, they are completely absent from these deep anoxic waters. Consequently, wooden shipwrecks that sank centuries ago remain nearly perfectly preserved on the Black Sea floor, retaining delicate carvings, tool marks, and structural integrity that would have been destroyed in oxygenated marine environments within decades.

Based on the passage, ancient wooden shipwrecks remain remarkably preserved at the bottom of the Black Sea because:

  1. wood-boring organisms cannot survive in the oxygen-depleted deep waters.Answer
  2. B
    the high density of incoming Mediterranean salt water prevents physical erosion of the timber.
  3. C
    the absence of wood-boring organisms causes atmospheric oxygen to stay near the surface.
  4. D
    freshwater rivers introduce chemical compounds that shield the wood from decay.

Answer

Wood-boring organisms cannot survive in the oxygen-depleted deep waters.
The second paragraph directly links the preservation of wooden shipwrecks ('Consequently, wooden shipwrecks... remain nearly perfectly preserved') to the fact that wood-boring organisms require oxygen to survive and are absent from deep anoxic waters.

Step-by-Step Solution

1
Locate the stated cause of shipwreck preservation in the text.
The second paragraph explicitly states: 'Because wood-boring organisms... require oxygen to survive, they are completely absent from these deep anoxic waters. Consequently, wooden shipwrecks... remain nearly perfectly preserved'.
ACT Reading literal cause-and-effect questions require identifying direct statements of cause directly linked to stated consequences.
2
Match the explicit cause with the correct option.
The option stating that wood-boring organisms cannot survive in oxygen-depleted deep waters directly paraphrases the explicit cause.
The absence of oxygen prevents wood-boring organisms from living there, which directly allows the wooden structures to endure.

Key Concept

Recognizing Explicit Cause and Effect
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Topics

Recognizing Explicit Cause and Effect

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