challenge: What was the primary reason why U.S. insurers began issuing reservation of rights letters in response to third-party claims by insureds?
  
  A. To increase premiums for policyholders who file frequent claims
  B. To discourage policyholders from filing frivolous claims
  C. To protect themselves from potential liability for damages in excess of policy limits
  D. To expedite the claims process and reduce paperwork
  Answer: 