What is the easiest way to explain what a stimulus is?

You are traveling down the road and the hopd flies up- a. look out of the gap between hood and cowling b. look out the left window c. stop the car d. turn on your four-way flashers e. use stop signal given with arm 2. you are driving down a dark, country road and the headlights suddenly go out- pull off the side of the road and stop flash your break lights activate your four way flasher have scotty beam you up turn your parking lights on 3. you turn on a crowded street and the accelerator pedal sticks- turn ignition off shift to neutral apply the brakes reach down and pull pedal by hand use the of toe of your food to pull pedal up

Although animals share many common characteristics, there is also a great amount of diversity found in animals. which animals are ectothermic, obtain dissolved oxygen in water through gills, have scales, have fins, and live in water?

Can someone give me one specific health problem, and explain it. !