Ashort piece of dna or rna onto which dna polymerase begins to add nucleotides
a. leading strand
b. okazaki fragment
c. primer
d. clamp-loading complex

Primer

Explanation:

DNA polymerase can't start adding nucleotides without having something to "hold on" to. This is why it needs a small fragment of DNA or RNA that binds the DNA template where it needs to be copied. Without this primer, DNA polymerase doesn't work.

c. primer

Explanation:

DNA polymerases are enzymes that carry out DNA replication. This enzyme cannot initiate the synthesis of the new chain, therefore, a short fragment of RNA that is called a primer must be created and must be matched to the chain that will be used as a template. Thus, the DNA polymerase enzyme begins to add nucleotides from the first one extending the 3 'end of the existing chain.

b is the best answer for this question.