Please, someone help me with the name of this chain

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

Which of the following is true for the actual yield of a reaction? it is always calculated as a ratio. it is the yield from the excess reactant. it is the yield from the limiting reactant. it is always less than the theoretical yield.

The same side of the moon always faces earth because the