Let us make a food chain with some theory.
Take a herbivorous animal for example a Deer. Grass is eaten by Deer, so we get this food chain:
A carnivorous animal like a Lion eats Deer, so we expand it.
We have a full chain.
Now we conculde that A Food chain begins with a producer because a herbivorous consumer consumes a producer, and ends with a carnivorous consumer because A herbivore figures along the middle.