Question

people need peat because its a source of fuel. they remove it from bogs with machines. imagine going to work to dig up peat and finding a thousand - year - old body! people have found other surprising things in bogs too, like books, tools, and weapons. once they found butter that was so well preserved you could still eat it—if you wanted to.
this 27 - pound lump of bog butter was unearthed in 2016.

Explanation:

The text says people remove peat (a fuel source) from bogs with machines and sometimes find bog bodies. The other options (finding while removing machines - no, digging for tools/weapons - not mentioned as main way, looking for bog butter - not the main context) are incorrect. The key is that peat - digging (for fuel) leads to discovery.

Answer:

People find bog bodies when they dig up peat for fuel.