Which of the following is the BEST reason a general contractor requires subcontractors to name it as an additional insured and provide certificates of insurance?

解析

Additional insured status gives the upstream party defense and indemnity under the downstream party's policy for claims arising out of that party's work, and the certificate documents that the coverage was placed. (a) is the dangerous version of the idea: risk transfer supplements the general contractor's own coverage and never replaces it, and its own insurer will still be looking at the claim. (b) mixes insurance with lien priority, which is fixed by the mechanics lien statute and not by an endorsement. (c) crosses two lines of coverage — employee injuries are handled by each employer's workers' compensation policy, which additional insured status does not touch.