Need help answering these 2 questions (Mandala)

As our current atmosphere formed, the concentrations of various atmospheric gases fluctuated. match each gas with the explanation that best describes how its proportion changed during the evolution of the atmosphere.

Congress checks on the power of the presidency by overriding a presidential reversal or veto. debating the bill in both of the houses. making laws without presidential review. sending the bill back to several committees

Chen's research team randomly assigned some newborns and their mothers either to a breastfeeding promotion group (where breastfeeding was encouraged, but not required) or to a normal pediatric care group (where breastfeeding was neither encouraged nor discouraged). which research method did they use?