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In Apex, 'bulkification' is the practice of ensuring code can handle multiple records efficiently without hitting governor limits. Snippet A demonstrates the correct bulkified approach for this requirement. It first iterates through the opportunityList to collect all unique AccountId values into a Set. Then, it performs a single SOQL query to retrieve all relevant Accounts and their child Contacts using a subquery (Inner Join). This ensures that the code only consumes one SOQL query regardless of how many opportunities are in the input list.

Snippet B is syntactically incorrect and will fail to compile. In Apex, you cannot use dot-notation (like opportunityList.AccountId) on a List collection to retrieve a set of IDs from its elements. To access the AccountId of records within a list, you must iterate through the list or use a map. Even if corrected to use a proper ID collection, Snippet A is often preferred when you need the relationship context between the Account and its Contacts. Most importantly, Snippet A correctly identifies the need to extract IDs into a separate collection before querying, which is a fundamental requirement for writing scalable Apex. It avoids the 'Query in a loop' anti-pattern and adheres to the platform's execution model.

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