An RFLP can be created:. a) only by a mutation creating a new restriction enzyme recognition site b) only by a basepair change within the restriction enzyme recognition site c) only by a deletion removing a restriction enzyme reognition site d) by any mutational event that cretes or deletes a restriction enzyme recognition site e) only in RNA

Option B, only by a basepair change within the restriction enzyme recognition site

Explanation:

A restriction fragment length polymorphism (RFLP) consists of alternative alleles with varying sizes of restriction fragments. In the traditional RFLPs, base pairs were changes at the restriction sites. These restriction sites comprises of nucleotide sequences that are identified by restriction enzymes. In RFLP analysis, the restriction fragments are created when restriction enzyme divide DNA into fragments. These restriction fragments are then separated while gel electrophoresis.

Before the advent of PCR, RFLPs (which were predominant form of  DNA variation) were used to analyze linkages.  

Hence, option B is correct

b is the correct answer