The expression "this form of life" in paragraph 5 refer to?
A.Water-based life. B.oxygen-based life. C.Methane-based life. D.Liquid-based microorganisms.
参考答案:
答案解析:
Among the elements of noble gases Helium is the___.
Among the elements of noble gases Helium is the___. A.lightest B.reactive C.impo