TOEFL Listening: ETS-TOEFL听力机经 - RO82LF4K15V3S0M3P$

What point does the professor make when she mentions the increase in biofilm research? A. The results of prior research have been controversial B. Prior research has focused on the benefits of biofilms C. Biofilms are difficult to remove D. Biofilms have become a major contributor to pollution