题目内容：

    Salty water just below the surface of Mars could hold enough oxygen to support the kind of microbial （微生物的） life that existed and developed quickly on Earth billions of years ago， researchers reported on Monday.

In some locations， the amount of oxygen available could even keep alive a primitive， multicellular （多细胞的） animal such as a sponge （海绵动物）， they reported in the journal Nature Geosciences. "We discovered that brines-water with high concentrations of salt - on Mars can contain enough oxygen for microbes to breathe，" said lead author Vlada Stamenkovic， a theoretical physicist at the Jet Propulsion Laboratory in California. "This fully revolutionizes our understanding of the potential for life on Mars， today and in the past. "

Up to now， it had been assumed that the trace （微量） amounts of oxygen on the Red Planet were insufficient to sustain even microbial life. "We never thought that oxygen could play a role for life on Mars due to its rarity in the atmosphere， about 0.14 percent，" Stamenkovic said. By comparison， the life-giving gas makes up 21 percent of the air we breathe.

On Earth， aerobic-that is， oxygen breathing -life-forms evolved （净化） together with photosynthesis （光合作用）， which converts CO2 into O2. The gas played a critical role in the existence of complex life， known after the so-called Great Oxygenation Event some 2.35 billion years ago.

But our planet also holds microbes -at the bottom of the ocean， in boiling hot springs -that live in environments lack of oxygen. "That's why -whenever we thought of life on Mars -we studied the potential for anaerobic （无氧的）life，" Stamenkovic said.

1.The underlined word "insufficient" in Para. 3 means " ______ ".

A.enough B.not enough

C.wrong D.right

2.Vlada Stamenkovic may agree that ______ .

A.this research changes people's understanding of the potential for life on Mars

B.the life-giving gas makes up 31 percent of the air people breathe on earth

C.Great Oxygenation Event happened some 2.35 million years ago

D.earth holds microbial life at the bottom of the desert

3.The main idea of the passage is ______ .

A.Mars is fit for living

B.multicellular animals are living on Mars

C.oxygen plays a role for life on earth

D.Mars is likely to have enough oxygen to support life