天山-3-Q30

T-3-Q30.
                

Unlike that of earlier works on slavery, Blassingame’s innovative study relies not on the records of White slave owners but on the records of the slaves themselves, especially the 70 or so autobiographies and memoirs that have been preserved.

1. that of earlier works on slavery, Blassingame’s

2. that of earlier works on slavery, Blassingame in his

3. earlier works on slavery, Blassingame in his

4. earlier works on slavery, Blassingame’s

5. the earlier works on slavery, Blassingame in his

弱问A中的that of 指什么？是指study么？为什么D 不对呢~请教