1. For a trait to increase in a population by natural selection, it must
a. be controlled by genes.
b. result from a new mutation.
c. help organisms adapt to their environment.
d. two of the above

I'm pretty sure it is d)

Explanation:

for a trait to undergo positive selection, it must have two characteristics. first the trait must be beneficial, in other words it must increase the organisms probability of surviving and reproducing. Second, the trait must be heritable so that it can be passed to an organisms offspring.

maybe because its impossible for balloons to lift a whole entire house.