• is correct because both (A) and (R) are true and (R) provides the exact breeding rationale: In highly heterozygous perennial fruit trees (e.g., mango, citrus, apple), identifying an elite superior bud sport or natural seedling mutant allows the breeder to capture both additive and non-additive (heterotic) gene actions in a single selection event, fixing them permanently via grafting without generation-by-generation inbreeding.
• is incorrect because Reason (R) directly explains why clonal selection is preferred.
• is incorrect because Reason (R) is correct.
• is incorrect because Assertion (A) is correct.

Training systems in viticulture:

• The Head system (bush system) is inexpensive and best suited for cultivars of low vigor (e.g., Beauty Seedless, Delight) where vines can support themselves on short stakes without extensive trellising.
• The Telephone system (T-trellis) has a 3-wire overhead crossarm, providing excellent canopy spread and light penetration for moderately vigorous cultivars that display pronounced apical dominance.
• Both statements are established viticultural facts, making Statement (I) and Statement (II) both true.

Pollination biology of apple (Malus domestica):

• Apple cultivars are predominantly self-incompatible (gametophytic self-incompatibility) and require pollen from cross-compatible diploid varieties blooming simultaneously. To secure adequate pollination throughout the orchard, standard pomological recommendations specify that at least $33\%$ (one-third) of the trees in commercial orchards must consist of suitable pollinizer cultivars.
• Reason (R) states the universal pomological principle that cross-pollinated fruit crops necessitate compatible pollinizer varieties blooming at the same time to achieve effective pollination and commercial fruit set.
• Both (A) and (R) are true, and (R) provides the accurate scientific explanation for (A).