Which of the Following Scenarios May Produce an Active Trend

Essay

Which of the following scenarios may produce an active trend in evolutionary change? Briefly justify your answer.
A. The mechanic stability of the exoskeleton of a group of terrestrial arthropods imposes an upper limit on the body size of these organisms.
B. The evolution of an endoparasitic lifestyle results in overall smaller body size as parasite species diversify to utilize small-bodied hosts, which are more common than large-bodied hosts.