机体的内环境指的是

A．体液

B．细胞内液

C．细胞外液

D．细胞内液+细胞外液

E．血液

— Are you familiar(熟悉) with the music?

— Yes. There was ______ time _____ this kind of music was quite popular. [ ]

A. a, that

B. a, when

C. the, which

D. the, when