Answer:
Cytochrome c is an enzyme found in bacteria, fungi, plants and animals. Here it is given that the human amino acid sequence for cytochrome c differs at 12 locations from the sequence in horses and pigeons. This information might be useful for inferring in preliminary stages that horses and pigeons are closely related to each other since they both show similar amount of difference from humans.
However, this hypothesis is being made with respect to the the comparison between "humans and horses" and "humans and pigeons". To further test this hypothesis pigeons and horses should be directly compared to each other without the use of a third species like humans. Hence, the sequence for cytochrome c in horse and pigeon should be compared with each other rather than comparing to humans.
Answer:
I think it might be A. I'm not sure.
The correct answer is D. Salt water.
Explanation
The hydrosphere is the system that groups all the waters of the earth that include oceans, seas, rivers, lakes, lagoons, frozen waters like ice and snow, among others. The water of the earth can be classified between salt water and freshwater, within the first group we find the oceans and the seas that represent two thirds of the total water of the earth, that is, 93 percent of the total water of the earth, a figure close to 1 370 323 000km³; the rest of the water is fresh and consists of rivers, lakes, lagoons, streams, groundwater, and glaciers. So, the correct answer is D. Salt water
The mitochondria converts food into energy
