Answer: The correct option is c. Segmentation evolved more than once in different branches of the cladogram.
Phylogenetic studies help to identify and understand evolutionary relationship between different life forms. It uses a diagram called as Cladogram to represent the branching of the evolutionary relationships. In cladogram studies each branching point tells a fundamental character of the evolutionary significance. Cladogenesis separates the gene pool by splitting into two or more than two separate pools each of which gives rise to one or more new species. Segmentation implies repeated parts and many animals consist of such repeated parts. Therefore, segmentation appears more than once in different cladogram branches.
People can be immunised against a pathogen through vaccination. Different vaccines are needed for different pathogens. For example, the MMR vaccine is used to protect children against measles, mumps and rubella (German measles).
