Which definition describes a half-life

The statement that most describes one way global winds affect weather and climate is a. polar easterlies move cool air to mid-latitudes. this is correct because the closer an area is to the equator the hotter it is, therefore if the polar winds are being moved towards the mid-latitudes it cools them down. 

Large asteroid and comet impacts. because they can have a huge impact on the environment, such as a loss of land, and crust on the earth with the big holes they produce. on the other hand, volcanic eruptions can also cause change within the environment by producing land, but im actually not quite sure which one would be a better answer, hopefully you read this and didnt just flat out choose the first sentence i have spoken! your welcome~