The theories on the expansion of the universe ?

a. may harm science if proved invalid
b. may be proved invalid by new discoveries
c. are weakened by frequent examinations
d. are too durable to change when re-examined

Theories are often the best explanations of natural phenomena we currently have. Yet, what one has to realize is that science is ever changing. That is why (B) is the correct answer, as new examinations, experiments, and discoveries could change some of these well-accepted theories. There is no way to "harm science" with viable observations and discoveries so (A) is incorrect. Answer (D) is also wrong since there is no assurance that a theory will never change in the future as they are merely accepted hypotheses.  Answer (C) is not the best answer since theories are usually well supported and wouldn't be veritable if every examination proved flaws. 

Hope this helped! :)

Other organisms can change their behavior to take the place of the plants in the ecosystem.