Input: Identify the most salient words:

a food chain shows how energy is transferred between organisms

Output: energy
organism
transfer

Input: Identify the most salient words:

balloons of various colours floating up the sky

Output: balloon
colour
float
sky

Input: Identify the most salient words:

sheep grazing on a farm

Output: farm
graze
sheep

Input: Identify the most salient words:

Airplanes flying in formation with smoke coming from their tails.

Output:
come
fly
formation
smoke