Researchers found a strain of E. coli bacteria that had mutation rates one hundred times higher than normal. Which of the following statements correctly describes the most likely cause of these mutations?

• A. The single-stranded binding proteins were malfunctioning during DNA replication.
• B. There were one or more mutations in the RNA primer.
• C. The proofreading mechanism of DNA polymerase was malfunctioning.
• D. The DNA polymerase was unable to add bases to the 3′ end of the growing DNA strand.