Question

carcinization, or the evolution of a crablike body form, has taken place in crustaceans many times over the last 250 million years. carcinization has occurred several times as well, even though it involves the loss of traits such as sideways walking that seem to have helped carcinized groups persist in a variety of ecosystems. in a 2021 paper, joanna wolfe and team note that many decarcinized groups are extinct and have very few living relatives—signs that decarcinization might be an evolutionary dead - end. but the team also discusses frog crabs, a living decarcinized group with traits suited to dwelling in sediment; fossils show that the group had decarcinized members as far back as the early cretaceous. this example suggests that ______. which choice most logically completes the text? a. the evolutionary benefits of a crablike body form are less certain than many studies of carcinization had previously implied. b. despite having many living relatives, some decarcinized groups did not benefit from decarcinization. c. sideways walking may have been less important to the survival of frog crabs than a protected abdomen and other traits associated with carcinization. d. a crablike body form may not be optimal in all cases, with ecological conditions sometimes favoring the persistence of decarcinization.

Explanation:

The text says decarcinization was seen as an "evolutionary dead - end" as most decarcinized groups are extinct or have few relatives. But frog crabs (a decarcinized group) have existed since the Early Cretaceous. This shows that in some ecological conditions, decarcinization can persist, meaning a crablike body form isn't always optimal. Option A: The text doesn't talk about previous studies' implications on carcinization benefits. Option B: Frog crabs have existed long, so decarcinization benefited them, and the text says most decarcinized groups have few living relatives, so B is wrong. Option C: The text doesn't compare sideways walking with other traits for frog crabs. Option D fits as the frog crab example shows decarcinization can persist in some conditions, so a crablike form isn't always best.

Answer:

D. a crablike body form may not be optimal in all cases, with ecological conditions sometimes favoring the persistence of decarcinization.