D because where there is deep n stuff
Answer: conservative model
Explanation: DNA isolated after one generation produced a single band which was a higher and intermediate in density between the heavy and light Nitrogen isotopic DNA used, showing that the first generation was a hybrid DNA. This observation fit with the dispersive and semi-conservative models only. And so at this generation, the conservative model was discarded.
Zambia
The other three are already well established.
Testosterone is the principal male sex hormone.