Is a post oak tree is a autotrophic or heterotrophic

All plants are autotrophic.

Autotrophic means he doesn't need another living thing to live (for eating) but that he makes his own food (photosynthesis). (auto means itself).

Heterotrophic means he needs others to keep on living. Like animals. All animals need to eat and can't make their own food with only sunlight, CO2 and water. They need food, which may be plants or other animals. That depends on the animal.