Answer:
Heart valves or the closure of the mitral and tricuspid atrioventricular (AV) valves at the beginning of ventricular systole and the closure of the aortic valve and pulmonary valve at the end of ventricular systole.
Explanation:
The heart tone “lub,” or S1, is caused by the closure of the mitral and tricuspid atrioventricular (AV) valves at the beginning of ventricular systole.
The heart tone “dub,” or S2 ( a combination of A2 and P2), is caused by the closure of the aortic valve and pulmonary valve at the end of ventricular systole.
The correct term for on female arctic fox would be "organism". Although it should be noted that this depends somewhat on the context of the environment.
It is phenotype becoz smoothness is outer character
"Are deer eating most of the young hemlocks?"
This is because, by reading the data on the forest, she was able to determine that the deer population's increase has caused the Hemlock's population to decrease because the deer eat the young Hemlocks.
