An important reason for auditors to obtain a good knowledge of a client's industry is that

A payroll processing functions could differ from client to client.

organizations like city governments have unique accounting requirements that could be complex.

$($C$)$ detection risk must be set in accordance with the needs of the industry as well as of the individual client.

$($D$)$ control risks will vary from zero to $100\%$ and can be better assessed in context.