Final answer:
Vascular or conductive tissue, including xylem and phloem, is a distinctive feature of complex plants. Therefore, the correct option is A.
Step-by-step explanation:
The statement is correct in highlighting this feature. The reason is also accurate, as vascular tissue is essential for the survival of complex plants in terrestrial environments.
Vascular tissue allows for the efficient transport of water, minerals, and nutrients throughout the plant, providing support and enabling the development of larger and more complex structures. The evolution of vascular tissue was a key adaptation that contributed to the success of complex plants in terrestrial habitats.
Therefore, the correct option is A.