In Apache Spark, the DataFrame.join() method is the correct way to perform a left join by specifying the how parameter as "left" or "left_outer". The crossJoin() method creates a Cartesian product, not a left join. The merge() method is not part of Spark's DataFrame API but is from pandas. The leftJoin() method does not exist in Spark's DataFrame API, and there is no standalone join() function in Spark; the join() method is called on DataFrame objects. Therefore, the correct answer is A.