Correct Answer: B
SQLite3::Database.new('database.db') is the correct way to create a new SQLite3 database connection. This creates a new Database object that represents the connection to the SQLite file.

Correct Answer: B
Prepared statements prevent SQL injection attacks by separating SQL code from data, and improve performance for repeated queries by pre-compiling the SQL statement.

Correct Answer: B
The pg gem is the standard Ruby interface for PostgreSQL databases. It provides comprehensive access to PostgreSQL features and is actively maintained.

Correct Answer: B
mysql2 is the recommended gem for MySQL connections. It's faster and more feature-complete than the older mysql gem, providing better performance and Unicode support.

Correct Answer: B
In Sequel, .where() is used to filter records. You can chain multiple .where() calls to add additional conditions, which are combined with AND logic.

Correct Answer: B
When an exception is raised inside a transaction block, the transaction is automatically rolled back to maintain data integrity. This ensures that partial changes are not saved to the database.

Correct Answer: C
Using parameterized queries with db.execute("SQL", [params]) is the safest approach. The database engine handles escaping and prevents SQL injection attacks by separating the SQL structure from the data.

Correct Answer: B
many_to_one represents a "belongs to" relationship in Sequel. For example, if a Post belongs to a User, you would use many_to_one :user in the Post model.

Correct Answer: B
Connection pooling improves performance by reusing existing database connections instead of creating and destroying connections for each request, which is an expensive operation.

Correct Answer: B
Raw SQL is often preferred for complex queries that are difficult to express in ORM syntax, performance-critical operations that need fine-tuning, or when using database-specific features that the ORM doesn't support.

Correct Answer: B
Database migrations manage schema changes over time in a versioned, trackable way. They allow teams to apply database changes consistently across different environments and roll back changes if needed.

Correct Answer: B
This creates a dataset (lazy query object) that, when executed, will return up to 10 users whose age is between 25 and 35 (inclusive), ordered alphabetically by name. The query isn't executed until you iterate over it or call a method like .all.