The blot technique is used to find an rna fragment within a sample that is complementary to a dna probe.

Northern blotting.

Explanation:

The northern blotting may be defined as a laboratory techniques for the identification of the RNA molecule. The northern blotting technique was discovered by James Kemp, James Alwine and George Stank.

The northern blotting technique is mainly used to determine the RNA fragment from a sample that complementary to DNA probe. The molecules can be separated by gel electrophoresis and later allowed to hybridize a probe.

Thus, the correct answer is northern blot.