Changes in the environment that cause an organism to respond are called?

Anything in the environment that causes a change is called a stimulus.

Explanation:

Organisms react to many stimuli, including light, temperature, odor, sound, gravity, heat, water, and pressure. The ability of living things to react to stimuli is known as irritability.

c. because step up transformer steps up the input voltage i.e increases the input voltage  

the number of turns are greater on the secondary side of step up transformer  

transformer does not handle dc current