GRE Reading Comprehension: ETS-GRE阅读ETS - 4684OG3M71SOHS6H7

According to the passage, the major problem currently facing scientists in the field of bio-materials is A. assessing and regulating the bonding between host tissue and implants B. controlling the transfer of potentially toxic materials across the interface of tissue and implant C. discovering new materials from which to construct implant devices D. deciding in what situations implants are needed E. determining the importance of short-term implants to long-term stability of tissue implant interfaces