In a 2019 study, Jeremy Gunawardena and colleagues found that the single-celled protozoan Stentor roeseli not only uses
strategies to escape irritating stimuli but also switches strategies when one fails. This evidence of protozoans
sophisticatedly “changing their minds” demonstrates that single-celled organisms may not be limited to ______ behaviors.
aggressive
rudimentary
evolving
advantageous
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.