The correct operations are union() and coalesce(1).

• C. union(): Combines two DataFrames by appending rows without shuffling data. It is a narrow transformation as it simply stacks partitions.
• D. coalesce(1): Reduces partitions by merging existing ones without a full shuffle. Coalesce avoids shuffling by combining partitions locally where possible, even though moving to a single partition may involve data movement, it does not induce a shuffle (unlike repartition).

Other options:

• A. intersect(): Requires identifying common rows, which typically triggers a shuffle.
• B. repartition(1): Explicitly redistributes data via a shuffle.
• E. rdd.getNumPartitions(): Returns an integer (number of partitions), not a DataFrame.