According to the textbook:

• Abscisic acid (A) acts as a general plant growth inhibitor and stress hormone, helping seeds to withstand desiccation and other unfavorable growth factors .
• Ethylene (B) promotes female flowers in cucumbers, thereby increasing the yield .
• Gibberellins (C) promote bolting (internode elongation just prior to flowering) in beet, cabbages, and many plants with rosette habit .
• Cytokinins (D) promote nutrient mobilisation, which helps in the delay of leaf senescence .