sat-dog

Choice B is the best answer because it most logically completes the text’s discussion of single-celled organism behavior. As used in this context, “rudimentary” means basic or unsophisticated. According to the text, a study of the single-celled protozoan Stentor roeseli showed that the organisms can switch strategies for escaping certain stimuli, “sophisticatedly ‘changing their minds’” and using new strategies should other strategies fail. This context suggests that single-celled organisms may not be limited to behaviors that are basic or rudimentary, since the study showed that single-celled protozoans can respond complexly to irritating stimuli.

Choice A is incorrect because the text doesn’t suggest that single-celled organisms may not be limited to behavior that is “aggressive,” or threatening. Rather, the text suggests that single-celled organisms may not be limited to behaviors that are basic, since the study of Stentor roeseli showed that single-celled protozoans can respond complexly to irritating stimuli. Choice C is incorrect because the text doesn’t suggest that single-celled organisms may not be limited to behavior that is “evolving,” or advancing. Rather, the text suggests that single-celled organisms may not be limited to behaviors that are basic, since the study of Stentor roeseli showed that single-celled protozoans can respond complexly to irritating stimuli. Choice D is incorrect because the text doesn’t suggest that single-celled organisms may not be limited to behavior that is “advantageous,” or helpful. Rather, the text suggests that single-celled organisms may not be limited to behaviors that are basic, since the study of Stentor roeseli showed that single-celled protozoans can respond complexly to irritating stimuli.