The fourth statement is true..........
2 different elements- carbon and oxygen.............................
Silicon is a popular semi-conductor. The process of doping either creates an excess or lack of electrons. In the case of silicon, the dopant is arsenic which has greater valence electron than silicon. Arsenic then donates an electron resulting to an excess of electrons. A new type or better type of semi-conductor is created. Silicon conduct greater electricity.
The best answer is the last option.
If you mean: "genetic isolation" (not: "reproductive isolation"????);
then, this is an example of: "ecological isolation"; or, "geographic isolation" .
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