Brain researchers think that the best reason the brain might weight the present high and the future low when faced with a present-future tradeoff is that:

responding quickly and definitively to present rewards might have come with an evolutionary advantage.
people are naturally short-run thinkers.
the future is harder to visualize than the present.
people naturally think they may die in the future.
a and c

Responding quickly and definitively to present rewards might have come with an evolutionary advantage.

The future is harder to visualize than the present.

Explanation:

Brain researchers think that the best reason the brain might weight the present high and the future low when faced with a present-future trade off is that people respond quickly and definitively to present rewards might have come with an evolutionary advantage and because the future is essentially hard to visualize.

They do not know, neither can they comprehend what the future hold for them. Therefore, they try to make use of the present scenario and hope for it to stretch to the future.

answer; lags, push the econ below the natural level of output;