Which one of the following is used as a vector for cloning into higher organisms?

The correct option is A $Retrovirus$
Vector
Vectors are the DNA molecules which can carry the foreign DNA fragment into the host cells for cloning. Examples include plasmids and bacteriophages.

Features of vector
The following are the common features of vector:

• Origin of replication (ori) - It is a specific nucleotide sequence that initiates replication. Due to this the vector can undergo self replication giving rise to multiple copies of the desired gene in the host cell.
• Selectable marker - It must be present for the identification of the transformants and non-transformants.
• Sites for the action of restriction endonucleases- Recognition sites for restriction enzymes help in the cleavage of the vector helping in inserting the gene of choice.
• Carrying capacity - They must carry DNA inserts into the host cells.

Features of vectors used for eukaryotes
For cloning into higher organisms like eukaryotic cells, the vector requires the capacity to enter the host eukaryote easily and direct the host DNA to make copies of the carried foreign DNA.

$Salmonellatyphimurium$
$Salmonellatyphimurium$ is not used as a vector as it can be pathogenic to the host cells and a gene that is inserted directly into a cell usually does not function. It causes typhoid fever-like disease.

$Rhizopusnigricans$
$Rhizopusnigricans$ is a parasite in animals. It causes rhinocerebral mucormycosis. Therefore it cannot be used as a vector.

Retrovirus
Retrovirus has the ability to easily transform a normal cell into cancerous cells and hence it can be modified to be used as a vector for cloning of genes into higher organisms. The pathogenicity from the genetic material is removed in such cases (disarmed virus).

Baculovirus
Baculovirus are pathogenic viruses that infect insects and arthropods. They are used for pest control and to produce recombinant proteins.

Final answer:
c. $Retrovirus$