Comprehensive and Detailed 150 to 250 words of Explanation From Snowflake SnowPro Architect exam scope and all publicly documented material:
Search Optimization Service improves performance by maintaining additional search structures to accelerate selective predicates for supported query patterns. Two common reasons it may not help are (1) exceeding the predicate limit and (2) predicate mismatch. If queries include more predicates than SOS can leverage effectively (or beyond documented limits for the access path), Snowflake may not apply the optimization and will revert to normal micro-partition pruning and scanning behavior (Choice B). Predicate mismatch occurs when the query's filter conditions do not align with the SOS access path definition-examples include using different columns than those optimized, applying functions/casts that prevent using the access path, or using non-supported predicate forms-so SOS cannot accelerate those queries (Choice C). Semi-structured data alone does not inherently prevent SOS benefits; SOS can be used with certain patterns, including on some expressions, but it still must match the configured access path. Likewise, the presence of SEARCH functions is not the core issue; SOS is about access paths and supported predicates, not requiring SEARCH() usage.
Architecturally, this is why SOS should be selectively enabled for columns and predicate shapes that dominate high-cost workloads, and monitored/adjusted as query patterns evolve.