Cell wall is the outer permeable covering in all pants and almost all prokaryotes ! cell wall are mainly made up of cellulose , sometime by chitin!!
The given blank can be filled with External.
The stimulus is a physical entity, which can provoke the response in the body of an organism. The hiding of the organism under the rock in response to the predator is and a type of external stimuli, as in this case, the organisms hide themselves inside the rock in response to the predator, which is present outside the body of the organism.
