a. All are ornamental plants

b. All are phylogenic link species

c. All are prone to overexploitation

d. All are exclusively present in the Eastern Himalayas.

Answer: c. All are prone to overexploitation.

Explanation: Nepenthes is also known as the pitcher plant. It is an insect-eating plant. Psilotum is a pteridophyte and is used medicinally. Aconitum is a medicinal plant. Rauwolfia is also a medicinal plant. We see that all plants have different characteristics and are used because these plants are often exploited. Therefore, one characteristic common to all plants is that all these plants are prone to overuse.