The protostome developmental sequence arose just once in evolutionary history, resulting in two main subgroups—Lophotrochozoa an
d Ecdysozoa. What does this finding suggest? _____ Select one: a. These two subgroups have a common ancestor that was a deuterostome. b. The protostomes are a polyphyletic group. c. Division of these two groups occurred after the protostome developmental sequence appeared. d. The lophotrochozoans are monophyletic.