Zoologists have described two modes of development in animals in the clade Bilateria: (1) protostome development seen in animals in the clades Ecdysozoa and Lophotrochozoa, and (2) deuterostome development as in the phyla Echinodermata and Chordata. What criteria are used to distin- guish between these two modes of development?

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Explanation:

Deuterostome development is one in which the blastopore develops to become the anus while in protostome development, the blastopore develops to become the mouth in the animal. In addition, deuterostomes exhibit indeterminate cleavage with a dorsal hollow nerve cord while protostomes exhibit determinate cleavage with a solid ventral cord.

i think that c)gold was found there

but i am not sure

clumped distribution, because you'de have all of the population gathered in a relatively small are.

it's the most common because it provides protection and a mate for reproduction

example: humans, seeweed, cattles, etc.