GRE Text Completion: JiJing 1373-GRE填空机经1373题 - 7J6B2FI207ZELX77A

The first images of Jupiter's moon Callisto show bright regions of material, as if older and darker ice had slid downhill and exposed the ____________ ice underneath. A. ancient B. murky C. compact D. pristine E. grimy F. unblemished