Which human activity will have the MOST positive effect on the global environment?

Reducing air pollution across countries by enforcing stricter emissions laws

Explanation:

This will limit the amount of green house gasses in the air witch will slow down climate chance reducing the melting of the polar ice caps  

before, trains worked using the steam engine. thus, it uses heat so it is crucial to apply heat balance. the steam engine absorbs energy during the stage of boiling water. so, this is the endothermic reaction. when the steam is used to work the piston, it has to release this energy through running the train. the excess energy is released as an exhaust to the chimney. this is the exothermic process because it releases energy to the surroundings.