Stem Elongation and Hormones:
Stem elongation in plants is a complex process that is regulated by various plant hormones. Two key hormones that play a significant role in stem elongation are auxin and gibberellin.

Effect of Gibberellin:
- Gibberellin is a plant hormone that is known to promote stem elongation.
- It stimulates cell division and cell elongation in the stem, leading to increased growth.
- By promoting the synthesis of enzymes that break down cell walls, gibberellin helps in the expansion of cells in the stem, resulting in elongation.

Effect of Auxin:
- Auxin is another important hormone that influences stem elongation.
- It controls cell elongation by promoting cell expansion and division.
- Auxin also plays a role in maintaining apical dominance, which affects the growth of the main stem.

Interaction of Gibberellin and Auxin:
- Both gibberellin and auxin work together to regulate stem elongation.
- Gibberellin promotes cell division and elongation, while auxin controls the direction of growth and coordinates the overall growth pattern.
- The interaction between these two hormones is essential for the proper elongation of the stem.
Therefore, the correct answer is B) auxin and gibberellin as both these hormones play crucial roles in regulating stem elongation in plants.