10. echinoderms are most closely related to chordates because both are:

a)protostomes b) deuterostomes c)endotherms d)ectotherms

oceans

indian ocean

pacific ocean

atlantic ocean

arctic ocean

southern ocean

answer : haversian

[explanation: -(compact bone is organized as parallel columns, known as haversian systems, which run lengthwise down the axis of long bones. these columns are composed of lamellae, concentric rings of bone, surrounding a central channel, or haversian canal, that contains the nerves, blood vessels, and lymphatic system of the bone)]