TOEFL Reading: ETS-TOEFL阅读机经 - GKOFLTYC4HKFKC8QL$

Which of the sentences below best expresses the essential information in the highlighted sentence in the passage? Incorrect choices change the meaning in important ways or leave out essential information. A. This result showed that the chemical transforming principle in S pneumococci was passed on to future generations of S pneumococci. B. After exposure to the cell-free extract from the S pneumococci, R pneumococci strain cells acquired the ability to transform themselves into S pneumococci. C. The transformation of R cells by a cell-free extract of S pneumococci demonstrated the existence of a chemical transforming principle that brought about heritable change. D. This transformation showed that the characteristics that the S pneumococci possess are superior to the characteristics of R pneumococci.