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.

The atmosphere wasn’t strong enough to contain more oxygen when compared earths atmosphere today, the exosphere was full of rips and couldn’t contain enough oxygen to provide for land creatures, although aquatic earthlings could continue i exist in this environment