Comprehensive and Detailed Explanation From Exact Extract:
Contingency allowances should be larger during the earlier phases (such as schematic design) due to greater unknowns and potential design changes. As the design progresses and more details are defined, contingency can be reduced.
Varying contingency based on owner funds (B) is inappropriate.
Contingency during construction administration (C) is typically lower.
Doubling contingency for CM use (D) is not standard practice.
References:
ARE 5.0 PPD - Project Costs and Budgeting
The Architect's Handbook of Professional Practice, 15th Edition - Cost Estimating