The correct option is B Probe
A probe is a radiolabeled single-stranded DNA/RNA fragment used to search for a gene of interest or other DNA sequence.
The clone is a population of genetically identical individuals normally produced asexually or by vegetative reproduction.
A plasmid is an extrachromosomal small DNA molecule that can replicate independently. They are mostly found in bacteria but are also present in archaea and eukaryotic organisms.
A vector is an engineered DNA molecule that can serve to carry foreign genetic material into another cell to facilitate the expression of the foreign gene, for example - plasmids, cosmids.