The one factor common to all arthropods leading to their success is largely due to:

Correct option is B

The chitinous exoskeleton is considered the most crucial factor contributing to the evolutionary success of arthropods, a group that includes insects, spiders, crustaceans, and myriapods. This rigid external covering provides structural and functional advantages that have allowed arthropods to diversify and thrive in nearly all ecosystems on Earth.
��️ Advantages of the Chitinous Exoskeleton:
1. Protection:
· Acts as a mechanical shield against predators, environmental hazards, and desiccation (drying out).
2. Support and Muscle Attachment:
· Serves as a rigid framework for muscle anchorage, allowing for efficient movement and strength.
3. Prevention of Water Loss:
· Especially in terrestrial arthropods, it helps in retaining moisture, enabling survival in dry habitats.
4. Moulting (Ecdysis):
· Although rigid, it can be shed and regenerated, allowing growth and development through life stages.
5. Versatility and Adaptation:
· Can be modified into wings, claws, antennae, etc., supporting ecological diversity and specialization.
Explanation for Each Option
(a) Small size ❌
· While small size helps in habitat penetration and reproduction, it is not unique to arthropods and not the primary reason for their evolutionary success.
(b) Chitinous exoskeleton ✅
· Correct answer.
· It is common to all arthropods and provides mechanical, physiological, and ecological advantages, making it the key factor behind their success.
(c) Joint footedness (Arthropodia) ❌
· Jointed appendages aid in mobility and manipulation, but this trait alone does not account for their extensive adaptability and protection like the exoskeleton does.