In the given diagrams, A (spine) and B (tendril) are structures which are modifications of the stem. Then, probable examples of plants in which A and B can be observed, respectively, will be:

Step-by-step solution

Modifications of stem: 1 . Underground stems may modify to store food. Examples - potato, turmeric, ginger, Colocasia , zaminkand, etc. 2 . Stem may develop into tendrils (originating from axillary buds) for support. Examples - grapevines and gourds (cucumber, pumpkins and watermelons). 3 . Stems may develop woody and pointed thorns for protection from the axillary buds. Examples - Bougainvillea , Citrus. 4 . Stems may develop chlorophyll and perform photosynthesis. Examples - Opuntia (stem as flattened structures)