Name the hardest artificial substance known?

In which layer of earth do most earthauakes occur a_ inner core b_outer core c_mantle d_crust

Which of these sequences lists the correct order for the creation of sedimentary rock from sediment? a. deposition, burial, compaction, cementation b. burial, deposition, compaction, cementation c. compaction, deposition, burial, cementation d. cementation, deposition, burial, compaction

Acrystal that absorvd water from air is (blank)a. aqueousb. homogenousc. hygroscopicd. efflorescent