Changes to rivers and streams can happen naturally, but has increased over the years due to which kind of human activity?

a.) humans build dams and redirect water flow.
b.) humans are using more land for agriculture.
c.) humans are using more energy efficient appliances.
d.) humans are using natural chemicals in factories.

Changes in the Rivers and Streams happens naturally but due to the human interventions it increased in an uneven way. There can be many reasons associated with it but the most appropriate answer would be the construction of dam and the redirection of the water flow.

There are many changes done when the construction of dam is done, sometimes the natural direction of water flow is changed and hence, it causes changes in the rives and streams.

There are chances that the redirected river or stream may become completely dry and this will be caused only due to redirecting the natural flow of river.

multiple allele inheritance is traits controlled by more than 2 alleles (ex: pigeons having 3 alleles of one gene govern their feather color).   so the answer is a.