GRE Text Completion: ETS Fundamental-GRE填空ETS基础 - 96GXV4JZ1LLV44K5X

One reason why pertinent fossils are (i)____________ is that crucial stages of evolution occurred in the tropics where it is difficult to explore for fossils, and so their discovery has (ii)____________. A. uncommon B. lagged C. recent D. declined E. unconceivable F. resumed