Anything within an environment that causes a response in an organism a.) long-day plants b.) short-day plants c.) tropism d.) stimulus

Keep in mind I'm answer based on the definitions I know.

Stimulus can be described as anything within an environment that causes a response in an organism.

I like to put this in a more every day sense.

When someone pokes you on an unknown site that doesn't begin with F, and you respond, you are being stimulated.

Pleas let me know if you find errors in my answer.

We can use solar powered cars or ride bikes instead of cars that burn fossil fuels

Carbon dioxide is the correct answer