（2010·安徽师大附中高三二模） 21．Some of the exercises appear to be _____ones that you have done, but after taking ____second look, you will find that they are different.
A. /, the B. the, the C. the, a D. /, a
（2010·安徽师大附中高三二模） 21．Some of the exercises appear to be _____ones that you have done, but after taking ____second look, you will find that they are different.
A. /, the B. the, the C. the, a D. /, a
C