TOEFL Listening: ETS-TOEFL听力机经 - 3DLA5JOKESUM4933P$

According to the professor, what problems must researchers solve before graphene can be used commericially? A. How to attach graphene to existing semiconductors B. How to mass-produce large sheets of graphene C. How to regulate graphene's electrical conductivity D. How to prevent graphene from sticking to surfaces