Which lung structure is a tiny sac that functions as an interface for gas exchange between air and blood?

he forelimbs below belong to four species that descended in a direct line from the ancestral mammal shown above. of the four descendants shown, which species most likely appeared earliest in evolutionary history?

evidence and logical support is essential for a scientist to do in order to maintain credibility. this is because no one can believe without any logic and without any evidence.hence a scientist can maintain credibility by proving himself and by answering logically so experiments prove very beneficial. logical hypothesis give conclusion which is acceptable. therefore, there are two main factors to maintain credibility by a scientist is evidence and logical support.

transformative rocks are the stones that emerge from the transformation of existing rock composes in a procedure called changeability, implies changing of structures. transformative rocks are shaped from alternate shakes that are changing a result of warmth or weight connected. one of this model is the earth developments that making rocks profoundly cover or crushed which will make the stones warmed and put under awesome weight. they are not softening but rather the minerals they are containing are changed synthetically that will shape transformative rocks. now and again different rocks are shaped when the others are near some liquid magma and getting warmed.