Question

which event of the near future would increase the likelihood of the lowest possible temperature increase?
a scientist uses a computer model to predict that earths average temperature will increase between 1.8°c and 3.2°c by the year 2100. the precise increase in temperature depends on peoples decisions in the future.
global emissions of greenhouse gases decrease by 50%
a major volcanic eruption strikes somewhere on earth
new technology reduces consumer prices for coal, oil, & natural gas
global emissions of cfcs decrease by 50%

Explanation:

Greenhouse gases (like carbon dioxide) trap heat in the Earth's atmosphere, contributing to global warming. If global emissions of greenhouse gases decrease by 50%, there will be fewer of these heat - trapping gases in the atmosphere. Fewer greenhouse gases mean less heat is trapped, which would lead to a lower increase in Earth's average temperature.
A major volcanic eruption can have a short - term cooling effect (due to aerosols blocking sunlight), but it is a short - term and less controllable/unpredictable event compared to reducing greenhouse gas emissions. New technology reducing prices for fossil fuels (coal, oil, natural gas) might encourage more use of these fossil fuels, which emit greenhouse gases when burned, leading to higher temperature increases. CFCs (chlorofluorocarbons) mainly affect the ozone layer, not directly the global temperature increase in the same way as greenhouse gases.

Answer:

global emissions of greenhouse gases decrease by 50%