Below the topsoil of the earth is the subsoil, _____ layer that contains stones mixed with a small amount of _____ organic matter.
A.a; the | B.the; the | C.不填; 不填 | D.a; 不填 |
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Below the topsoil of the earth is the subsoil, _____ layer that contains stones mixed with a small amount of _____ organic matter.
A.a; the | B.the; the | C.不填; 不填 | D.a; 不填 |