How can scientists know for sure that the cell theory is true? what evidence do we have to prove it?

The cell theory is still a theory because there is still no proof of how the first cell was formed. Also, the cell theory isn't unanimously accepted worldwide.

if you break down the data from the global footprint network, china exerts far more pressure on its ecosystems per capita than america in terms of crops, grazing, foresting, and fishing. but where america blows everybody out of the water is carbon emissions per capita