According to the textbook:

• Ethylene (A) promotes senescence and abscission of plant organs, especially leaves and flowers .
• Cytokinins (B) promote nutrient mobilisation which helps in the delay of leaf senescence .
• ABA (Abscisic Acid) (C) inhibits seed germination and plays a role in dormancy .
• Gibberellins (D) cause an increase in the length of the axis (stem), used to increase the length of grape stalks or sugarcane stems .