Answer:
B. atrioventricular (AV) valve
Explanation:
The function of the conduction system of the heart is to spread the electric signal and make the heart contract in coordinated timing. Conduction starts at SA node, then the AV node then will spread by bundle branches.
The atrioventricular valve is not part of the conduction system. The valve function is to keep the blood flow back. If the valve is broken and blood did flow back, it can make the heart need to do more work than usual.
Flatworm get most of their oxygen through diffusion.
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I would say A, B D are the correct answers
C hope this helps. ............
