Animals in which the first opening of the embryo is the mouth are called

stimulus is a change in the environment that causes an organism to react. the response is the reaction to the stimulus. some examples of stimuli for zebras are drought, to many predators, and bad feeding grounds such as dead grass or plants. zebras respond to stimuli just like all other living organisms

you should wear a lead protective shield when having teeth x-rays

hope i

-lavira : )