According to paragraph 3, why did Griffith conclude from his experiment injecting both R and S strains pneumococci into mice that some of the R strain bacteria transformed into disease-causing S strain pneumococci A. All the living bacteria he found in the blood of the injected mice were S strain bacteria. B. He already knew from earlier experiments that R strain pneumococci sometimes transform into S strain pneumococci. C. He could tell from examining the bacteria under a microscope that some individual pneumococci cells had characteristics of both the S and R strains. D. He observed living cells in the mice's blood with S strain characteristics, but the only living cells injected were R strain pneumococci.