GRE Text Completion: JiJing 1373-GRE填空机经1373题 - DYA38L7NJ316VWRLA

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). A. dearth B. a controversial C. presumption D. an unambiguous E. detection F. a possible