Which characteristic is common to both segmented worms and flatworms?
a) a flat body
b) a long, slender, round body
c) a front end and a back end
d) a segmented body

I believe it is C) a front end and a back end.

Apologies if I'm incorrect.

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)]

hydrogen is a compound or a single element and a element is a pure substence that cannot be separated into simpler subtances

clorine is a compound its a chemical substance that forms when two or more different elements combine

so both hydrogen and clorine are compounds