A grapevine growing around a fence post is an example of?

A - phototropism

B-photoperiodism

C - geotropism

D - thigmotropism

The answer is D - thigmotropism

Tropism is plant growth in a response to a stimulus.

Through the process of elimination:

A - phototropism is plant growth in a response to light.

B - Photoperiodism is an organism reaction to the lengths of days and nights.

C - Gravitropism is plant growth in a response to gravity.

D - Thigmotropism is plant growth in a response to contact

Since a grapevine makes a contact with a fence, this is an example of thigmotropism.