In preparing the engagement work program, which of the following is generally true with respect...

Comprehensive and Detailed Explanation:

Secondary controls are not primary risk mitigations but provide backup support if key controls fail. When preparing the work program, auditors generally focus on key controls, since they directly address significant risks. Secondary controls may not require testing unless they provide meaningful risk reduction where primary controls are weak or absent. Option A is inefficient; a separate work program for secondary controls is not required. Option C is incorrect — documentation alone does not make them essential. Option D is misleading because secondary controls are not subject to the same level of testing rigor as key controls. Therefore, Option B is correct: secondary controls do not always need to be tested.