Final answer:
Old World monkeys are best described as terrestrial, as they include ground-dwelling species alongside arboreal ones. They are not universally bipedal, nocturnal, or specialized for brachiation (arm-swinging).
Step-by-step explanation:
Old World monkeys, scientifically referred to as Catarrhini, have evolved distinct traits that reflect their habitat adaptations and are typically found in Africa and Asia. Unlike their New World counterparts, Old World monkeys do not possess prehensile tails but include both arboreal and terrestrial species. Their terrestrial nature is exemplified by species such as the rhesus macaque and Hanuman langur, some of which can adapt to urban environments by consuming human refuse.
When categorizing Old World monkeys based on the options provided in the question, the most accurate description is (a) terrestrial, as these primates include ground-dwelling species. They are not exclusively bipedal, nocturnal, or specialized for brachiation (arm-swinging), which are characteristics not broadly representative of Old World monkeys.