Answer:
B) Valves closing
Explanation:
A healthy heart makes a lub-dub sound with each beat. This sound comes from the valves shutting on the blood inside the heart. The first sound (the lub) happens when the mitral and tricuspid valves close.
Answer:
Time isint a concern for me but money is :/
Answer:
1) circulatory and respiratory
2) endocrine
3) circulatory
4) circulatory and nerves
Explanation:
I think these are right. Sorry if they are not.
