A:效应B细胞、抗原
B:效应细胞毒T细胞、抗体
C:效应细胞毒T细胞、效应B细胞
D:效应B细胞、效应细胞毒T细胞
Mary used to ________ to work, but she is used to ________ to work now.
下列说法正确的是( )