The cell wall . a)is thick and rigid b)is made of cellulose c)does not allow the transport of chemicals d)is only present in animal cells e)supports and protects the cell

i think it would be b. tissue because an organ system is a group of organs that work together to perform one or more functions. each does a particular job in the body, and is made up of certain tissues.

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

the correct answer is 2 and 4