Which of the following is not a heterotrophic organism?

Heterotrophic organisms are those organisms that cannot make their own food and depend on other sources like plants or animals for nutrition.

A cactus is a plant that carries out photosynthesis and prepares its own food. Since the plant grows in arid regions, its leaves are reduced to thorns and the green stems possessing chlorophyll, perform photosynthesis. 

Human beings, mice, and venus flytraps are examples of heterotrophic organisms.