The structure being described is the tricuspid valve.The right atrium is one of the two atria of the heart which function by receiving blood entering the heart, it is located to the right of the left atrium and superior to the much larger and more muscular right ventricle. Between the right atrium and right ventricle is a one way valve known as the tricuspid valve.
The answer is D proteins. viruses<span> contain nucleic acid, either DNA or RNA and a protein coat</span>
Animal pollinations give flowering plants reproductive advantages over gymnosperms. Take a bee for example. A bee may pollinate a flower, but the leftover pollen on the bee's body or wings can spread to other flowers.
When you think about it, structure is often but perhaps not always necessary for function of a certain ability in any organism.
Wings for example give organisms the ability to fly, so the structure of their wings enables them to fly. Without wings, they wouldn't be able to fly (excluding free fall or using technology).
Also important is too understand that we adapt through changing our abilities - function ever so slightly from generaton to generation to adapt to a certain environment where we live, this can then change structure accordingly to ensure proper function for the new ability.
