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Difficulty: EasyInferences from the Text

In the late twentieth century, glaciologists surveying the Antarctic ice sheet using airborne radio-echo sounding detected anomalous, flat, highly reflective interfaces deep beneath kilometers of solid ice. Because liquid water reflects radar waves far more intensely than surrounding glacial ice and forms a horizontal surface under hydrostatic pressure, researchers deduced that these subterranean signatures represented vast, isolated bodies of liquid water rather than anomalous bedrock formations. The existence of these subglacial lakes demonstrated that geothermal heat from the Earth's crust, combined with the insulating effect of thick overlying ice sheets and high overburden pressure that lowers the melting point of ice, is sufficient to maintain liquid water even in regions where surface atmospheric temperatures never rise above freezing.

Based on the passage, which of the following statements can be logically inferred? (Select all that apply.)

  1. Liquid water can persist beneath the Antarctic ice sheet even when surface atmospheric temperatures remain continuously subfreezing.Answer
  2. B
    Geothermal heat by itself is sufficient to maintain liquid lakes in Antarctica in the absence of thick ice sheets.
  3. Radio-echo sounding was able to distinguish subglacial water bodies partly because radar waves reflect differently off liquid water than off glacial ice.Answer
  4. D
    Most subglacial lakes discovered beneath the Antarctic ice sheet contain unique microbial ecosystems adapted to total darkness.
  5. E
    Solid glacial ice reflects airborne radar signals with greater intensity than liquid water under hydrostatic pressure.

Answer

The statements establishing that liquid water can persist beneath the ice sheet despite subfreezing surface temperatures and that radio-echo sounding detects water via differing radar reflectivity properties are both logically inferred from the text.
The passage explicitly supports both that liquid water can remain beneath the ice sheet despite subfreezing surface temperatures (stated in the final sentence) and that radio-echo sounding relies on the difference in radar wave reflectivity between liquid water and surrounding ice (stated in the second sentence).

Step-by-Step Solution

1
Analyze the passage for claims concerning surface temperatures and subglacial water persistence.
The final sentence demonstrates that geothermal heat, pressure, and ice insulation combine to maintain liquid water where surface temperatures never rise above freezing.
This directly confirms the validity of inferring that liquid water persists under subfreezing surface conditions.
2
Analyze how airborne radio-echo sounding identified subglacial lakes.
The passage states that researchers deduced liquid water because it reflects radar waves far more intensely than surrounding glacial ice.
This directly confirms the validity of inferring that detection relies on differing reflectivity properties between water and ice.
3
Evaluate remaining assertions against passage constraints and scope.
Claims regarding geothermal heat acting alone, microbial ecosystems, and higher reflectivity of solid ice represent unsupported extrapolations, outside knowledge, or direct factual reversals.
Eliminating invalid distractors leaves the two confirmed statements as the complete set of correct answers.

Key Concept

Deducing supported textual inferences while rejecting outside knowledge, quantifier misattributions, and inverted relationships.
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Inferences from the Text

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