Question

drag the missing word into place
oil in the ground, trees in the forest,
earth is chock - full of these resources.
but theyre never gonna last
reliable
protect
natural

Explanation:

Oil and trees are natural resources. "Natural" is the correct word to describe these resources. "Reliable" means trustworthy and doesn't fit the context. "Protect" is a verb and the blank requires an adjective.

Answer:

natural