For each blank select one entry from the corresponding column of choices. Fill all blanks in the way that best completes the text.
The (i)_____ of molecular oxygen on Earth-sized planets around other stars in the universe would not be (ii)_____ sign of life: molecular oxygen can be a signature of photosynthesis (a biotic process) or merely of the rapid escape of water from the upper reaches of a planetary atmosphere (an abiotic process).
dearth |
presumption |
detection |
a controversial |
an unambiguous |
Blank (i) |
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dearth |
presumption |
detection |
Blank (ii) |
---|
a controversial |
an unambiguous |
a possible |
Blank (i) |
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dearth |
presumption |
detection |
Blank (ii) |
---|
a controversial |
an unambiguous |
a possible |
Select one entry from each column.