回答：had been doing是过去完成进行时；had been +表语（名词、代词、形容词、有些副词、介词短语、非谓语动词等）是过去完成时、系表结构。如：He told us that he had been doing this research.He said he had been busy.
不能，这句只是过去完成进行时作谓语，不是主系表结构。
