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) |
|---|
| dearth |
| presumption |
| detection |
| Blank (ii) |
|---|
| a controversial |
| an unambiguous |
| a possible |
| Blank (i) |
|---|
| dearth |
| presumption |
| detection |
| Blank (ii) |
|---|
| a controversial |
| an unambiguous |
| a possible |
Select one entry from each column.