ProfessorBackmantookupscientificresearchfordecades(幾十年...

問題詳情：

 Professor Backman took up scientific research for decades (幾十年), and this is ______ he devoted all his life to.

A. which               B. what             C. where            D. how

【回答】

B

知識點：連詞

題型：選擇題