Which of the following statements about secondary professional liability insurance is correct?

Primary professional liability insurance provides the first layer of coverage up to stated limits for covered claims (often negligence-based errors and omissions). Secondary (or excess/umbrella) professional liability insurance is designed to add additional limits above the primary policy and may “sit over” the primary coverage once the primary limit is exhausted, subject to terms and conditions. It does not replace the primary policy (A), and it is not reserved only for sole practitioners (C); firms and individuals may purchase excess coverage depending on project risk and contractual requirements. Secondary coverage is not inherently “more comprehensive” in scope than primary coverage (D); it is typically more about increasing the limit of indemnity rather than expanding covered causes of loss (and it may follow the form of the primary policy). Therefore, the correct statement is that secondary professional liability insurance supplements primary insurance (B).